Hi there, i ve got an issue - plugin doesnt work with php 7.4 ("Call to undefined function mb_regex_encoding"), non K2 pages work correctly, with php 7.3 all is correct. Did anyone have it?
Joomla 3.9.14, К2 2.10.2

When tracing scripts, we observe the following:

13:11:13 lstat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/administrator/components/com_k2/table", 0x7ffdab26dd90) = -1 ENOENT (No such file or directory)
13:11:13 lstat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/administrator/components/com_k2/table/k2category.php", 0x7ffdab26dd90) = -1 ENOENT (No such file or directory)
13:11:13 stat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/administrator/components/com_k2/tables/k2category.php", {st_mode=S_IFREG|0644, st_size=6941, ...}) = 0
13:11:13 stat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/administrator/components/com_k2/tables/k2category.php", {st_mode=S_IFREG|0644, st_size=6941, ...}) = 0
13:11:13 stat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/administrator/components/com_k2/tables/table.php", {st_mode=S_IFREG|0644, st_size=555, ...}) = 0
13:11:13 sendto(5, "-\0\0\0\3SHOW FULL COLUMNS FROM `p1bev_k2_categories`", 49, MSG_DONTWAIT, NULL, 0) = 49
13:11:13 poll([{fd=5, events=POLLIN|POLLERR|POLLHUP}], 1, 86400000) = 1 ([{fd=5, revents=POLLIN}])
13:11:13 recvfrom(5, "\1\0\0\1\tF\0\0\2\3def\22information_schema\7COLUMNS\7COLUMNS\5Field\vCOLUMN_NAME\f-\0\0\1\0\0\375\1\0\0\0\0E\0\0\3\3def\22information_schema\7COLUMNS\7COLUMNS\4Type\vCOLUMN_TYPE\f-\0\364\377\v\0\374\21\0\0\0\0M\0\0\4\3def\22information_schema\7COLUMNS\7COLUMNS\tCollation\16COLLATION_NAME\f-\0\200\0\0\0\375\0\0\0\0\0E\0\0\5\3def\22information_schema\7COLUMNS\7COLUMNS\4Null\vIS_NULLABLE\f-\0\f\0\0\0\375\1\0\0\0\0C\0\0\6\3def\22information_schema\7COLUMNS\7COLUMNS\3Key\nCOLUMN_KEY\f-\0\f\0\0\0\375\1\0\0\0\0K\0\0\7\3def\22information_schema\7COLUMNS\7COLUMNS\7Default\16COLUMN_DEFAULT\f-\0\364\377\v\0\374\20\0\0\0\0@\0\0\10\3def\22information_schema\7COLUMNS\7COLUMNS\5Extra\5EXTRA\f-\0x\0\0\0\375\1\0\0\0\0J\0\0\t\3def\22information_schema\7COLUMNS\7COLUMNS\nPrivileges\nPRIVILEGES\f-\0@\1\0\0\375\1\0\0\0\0K\0\0\n\3def\22information_schema\7COLUMNS\7COLUMNS\7Comment\16COLUMN_COMMENT\f-\0\0\20\0\0\375\1\0\0\0\0\5\0\0\v\376\0\0\"\0M\0\0\f\2id\20int(11) unsigned\373\2NO\3PRI\373\16auto_increment\37select,insert,update,references\0I\0\0\r\4name\fvarchar(255)\17utf8_general_ci\2NO\0\373\0\37select,insert,update,references\0J\0\0\16\5alias\fvarchar(255)\17utf8_general_ci\2NO\0\373\0\37select,insert,update,references\0H\0\0\17\vdeion\4text\17utf8_general_ci\2NO\0\373\0\37select,insert,update,references\0\0\0\2\3def\16u0622208_admin\vp1bev_users\vp1bev_users\2id\2id\f?\0\v\0\0\0\3\3B\0\0\0B\0\0\3\3def\16u0622208_admin\vp1bev_users\vp1bev_users\4name\4name\f-\0@\6\0\0\375\t@\0\0\0J\0\0\4\3def\16u0622208_admin\vp1bev_users\vp1bev_users\10username\10username\f-\0X\2\0\0\375\t@\0\0\0D\0\0\5\3def\16u0622208_admin\vp1bev_users\vp1bev_users\5email\5email\f-\0\220\1\0\0\375\t@\0\0\0J\0\0\6\3def\16u0622208_admin\vp1bev_users\vp1bev_users\10password\10password\f-\0\220\1\0\0\375\1\0\0\0\0D\0\0\7\3def\16u0622208_admin\vp1bev_users\vp1bev_users\5block\5block\f?\0\4\0\0\0\1\t@\0\0\0L\0\0\10\3def\16u0622208_admin\vp1bev_users\vp1bev_users\tsendEmail\tsendEmail\f?\0\4\0\0\0\1\0\0\0\0\0R\0\0\t\3def\16u0622208_admin\vp1bev_users\vp1bev_users\fregisterDate\fregisterDate\f?\0\23\0\0\0\f\201\0\0\0\0T\0\0\n\3def\16u0622208_admin\vp1bev_users\vp1bev_users\rlastvisitDate\rlastvisitDate\f?\0\23\0\0\0\f\201\0\0\0\0N\0\0\v\3def\16u0622208_admin\vp1bev_users\vp1bev_users\nactivation\nactivation\f-\0\220\1\0\0\375\1\0\0\0\0F\0\0\f\3def\16u0622208_admin\vp1bev_users\vp1bev_users\6params\6params\f-\0\374\377\377\3\374\21\20\0\0\0T\0\0\r\3def\16u0622208_admin\vp1bev_users\vp1bev_users\rlastResetTime\rlastResetTime\f?\0\23\0\0\0\f\201\0\0\0\0N\0\0\16\3def\16u0622208_admin\vp1bev_users\vp1bev_users\nresetCount\nresetCount\f?\0\v\0\0\0\3\1\0\0\0\0F\0\0"..., 32768, MSG_DONTWAIT, NULL, NULL) = 1537
13:11:13 lstat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/cms/string/punycode.php", 0x7ffdab26d940) = -1 ENOENT (No such file or directory)
13:11:13 lstat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/joomla/string/punycode.php", 0x7ffdab26d940) = -1 ENOENT (No such file or directory)
13:11:13 lstat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/legacy/string/punycode.php", 0x7ffdab26d940) = -1 ENOENT (No such file or directory)
13:11:13 stat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/src/String/PunycodeHelper.php", {st_mode=S_IFREG|0644, st_size=5211, ...}) = 0
13:11:13 stat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/src/String/PunycodeHelper.php", {st_mode=S_IFREG|0644, st_size=5211, ...}) = 0
13:11:13 stat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/idna_convert/idna_convert.class.php", {st_mode=S_IFREG|0644, st_size=94950, ...}) = 0
13:11:13 stat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/idna_convert/idna_convert.class.php", {st_mode=S_IFREG|0644, st_size=94950, ...}) = 0
13:11:13 sendto(5, "\223\0\0\0\3SELECT `g`.`id`,`g`.`title`\nFROM `p1bev_usergroups` AS g\nINNER JOIN `p1bev_user_usergroup_map` AS m ON m.group_id = g.id\nWHERE `m`.`user_id` = 106", 151, MSG_DONTWAIT, NULL, 0) = 151
13:11:13 poll([{fd=5, events=POLLIN|POLLERR|POLLHUP}], 1, 86400000) = 1 ([{fd=5, revents=POLLIN}])
13:11:13 recvfrom(5, "\1\0\0\1\0029\0\0\2\3def\16u0622208_admin\1g\20p1bev_usergroups\2id\2id\f?\0\n\0\0\0\3#B\0\0\0?\0\0\3\3def\16u0622208_admin\1g\20p1bev_usergroups\5title\5title\f-\0\220\1\0\0\375\t@\0\0\0\5\0\0\4\376\0\0\2\0\16\0\0\5\0018\vSuper Users\5\0\0\6\376\0\0\2\0", 32768, MSG_DONTWAIT, NULL, NULL) = 169
13:11:13 stat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/src/Document/ErrorDocument.php", {st_mode=S_IFREG|0644, st_size=4809, ...}) = 0
13:11:13 stat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/src/Document/ErrorDocument.php", {st_mode=S_IFREG|0644, st_size=4809, ...}) = 0
13:11:13 stat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/templates/ser-vice/index.php", {st_mode=S_IFREG|0644, st_size=14183, ...}) = 0
13:11:13 lstat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/cms/text.php", 0x7ffdab26d800) = -1 ENOENT (No such file or directory)
13:11:13 lstat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/cms/text/text.php", 0x7ffdab26d800) = -1 ENOENT (No such file or directory)
13:11:13 lstat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/joomla/text.php", 0x7ffdab26d800) = -1 ENOENT (No such file or directory)
13:11:13 lstat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/joomla/text/text.php", 0x7ffdab26d800) = -1 ENOENT (No such file or directory)
13:11:13 lstat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/legacy/text.php", 0x7ffdab26d800) = -1 ENOENT (No such file or directory)
13:11:13 lstat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/legacy/text/text.php", 0x7ffdab26d800) = -1 ENOENT (No such file or directory)
13:11:13 stat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/src/Language/Text.php", {st_mode=S_IFREG|0644, st_size=11777, ...}) = 0
13:11:13 stat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/libraries/src/Language/Text.php", {st_mode=S_IFREG|0644, st_size=11777, ...}) = 0
13:11:13 stat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/templates/ser-vice/error.php", {st_mode=S_IFREG|0644, st_size=1839, ...}) = 0
13:11:13 stat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/templates/ser-vice/error.php", {st_mode=S_IFREG|0644, st_size=1839, ...}) = 0
13:11:13 stat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/templates/ser-vice/error.php", {st_mode=S_IFREG|0644, st_size=1839, ...}) = 0
13:11:13 stat("/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/templates/ser-vice/index.php", {st_mode=S_IFREG|0644, st_size=14183, ...}) = 0
13:11:13 chdir("/var/www/cgi-bin/cgi_wrapper") = 0
13:11:13 sendto(5, "\276\4\0\0\3UPDATE `p1bev_session`\nSET `data` = 'joomla|s:1044:\\\"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"..., 1218, MSG_DONTWAIT, NULL, 0) = 1218
13:11:13 poll([{fd=5, events=POLLIN|POLLERR|POLLHUP}], 1, 86400000) = 1 ([{fd=5, revents=POLLIN}])
13:11:13 recvfrom(5, "0\0\0\1\0\1\0\2\0\0\0(Rows matched: 1 Changed: 1 Warnings: 0", 32768, MSG_DONTWAIT, NULL, NULL) = 52
13:11:13 sendto(5, "\1\0\0\0\t", 5, MSG_DONTWAIT, NULL, 0) = 5
13:11:13 poll([{fd=5, events=POLLIN|POLLERR|POLLHUP}], 1, 86400000) = 1 ([{fd=5, revents=POLLIN}])
13:11:13 recvfrom(5, "\234\0\0\1Uptime: 10299491 Threads: 13 Questions: 2946793919 Slow queries: 0 Opens: 179159971 Flush tables: 1 Open tables: 4048 Queries per second avg: 286.110", 32768, MSG_DONTWAIT, NULL, NULL) = 160
13:11:13 sendto(5, "\1\0\0\0\1", 5, MSG_DONTWAIT, NULL, 0) = 5
13:11:13 close(5) = 0
13:11:13 setitimer(ITIMER_PROF, {it_interval={0, 0}, it_value={0, 0}}, NULL) = 0
13:11:13 fcntl(3, F_SETLK, {type=F_UNLCK, whence=SEEK_SET, start=0, len=0}) = 0
13:11:13 write(4, "\1\6\0\1\4\351\7\0Status: 500 Internal Server Error\r\nX-Powered-By: PHP/7.4.0\r\nX-Logged-In: False\r\nX-Content-Powered-By: K2 v2.10.2 (by JoomlaWorks)\r\nCache-Control: no-cache\r\nPragma: no-cache\r\nContent-type: text/html; charset=UTF-8\r\n\r\n\n\n\n\t\n\t\320\236\321\210\320\270\320\261\320\272\320\260: 0 Call to undefined function mb_regex_encoding()\n\t\n\t\n\n\n\n\n\t\n\t
\n\t\t
\n\n\t\t\t\n \t\t\t
\320\232 \321\201\320\276\320\266\320\260\320\273\320\265\320\273\320\275\320\270\321\216, \320\274\321\213 \320\275\320\265 \320\274\320\276\320\266\320\265\320\274 \321\201\320\264\320\265\320\273\320\260\321\202\321\214 \321\215\321\202\320\276. \320\237\320\276\320\277\321\200\320\276\320\261\321\203\320\271\321\202\320\265 \320\262\320\265\321\200\320\275\321\203\321\202\321\214\321\201\321\217 \320\275\320\260 \320\263\320\273\320\260\320\262\320\275\321\203\321\216
\n \t\t\t
\n \t\t\t
0\n \t\t\t Call to undefined function mb_r"..., 1288) = 1288
13:11:13 shutdown(4, 1 /* send */) = 0


The error occurs when working with the table of the following plugin:
/var/www/vhosts/u0622208.plsk.regruhosting.ru/httpdocs/tdmolot.ru/administrator/components/com_k2/tables/table.php

I think its not wrong installation, cause its works good with php 7.3.6. Issue comes only when php 7.3 to 7.4 has changed.
About permissions of joomla files - i can change it and group permissions enabled for read and execute/search, disabled for write.
About mbstring - provider says that already installed on web server.
Are you sure that K2 ver. 2.10.2 correctly works with PHP 7.4 now?

Provider says that mbstring module exists on web server:
~ $ /opt/php/7.4/bin/php -m | grep mbstring
mbstring

tdmolot.ru/i.php

Hi, you wrote earlier that i can re-install the plugin to fix the problem with php 7.4, so
how can I do it so that the all products pages are saved? All products page i have create in k2.