I have the same problem since updating. I was using one of the default themes. I’ve tried all themes from 12 to 20, same problem. I’ve tried Firstyme and Highstarter, same problem. I inserted the line remove_theme_support( ‘widgets-block-editor’ ); into the function.php, it worked for widgets, but I still couldn’t customise. Tried changing the theme, this line has no effect.
Seems to me it is a bug in the update, connected with the blocks in widgets feature, and needs to be fixed asap.
Any more suggestions, I’d be most grateful.
