I guess someone has already report this. But my solution is you made a shortcut for remove frame.

1. Go to Settings>Configure Krita
2. Go to Keyboard shortcut
3. Search remove frame. Then set up any key you want. I put F12 for it.

That's a useful mitigation solution. Thank you for mentioning it.

I've added this information to the bug report for this problem: https://bugs.kde.org/show_bug.cgi?id=392233