Using Joomla! 3.9.6 and the previous version, in combination with K2 2.9.0 I was getting a white screen on the add/edit screen. I saw in another thread to update to dev for PHP errors, so I am using K2 v2.10.0. Using PHP 7.2, the page is blank and the source looks like this:
cl.ly/d289f301c729
It works with PHP 5.6. The front-end works fine with either version, so it's just the admin edit screen.
Thanks!
Tarik