I've had this message since 5.2

[sooz]

That error message is telling you the Imagine Board plugin is not working.

It needs to be updated by the author for 5.2.

Krita 5.2 Release Candidate is out! Please help us in another round of testing!

The error’s being caused by the Imagine Board plugin needing to be updated for 5.2. You can disable the plugin from Preferences->Python Plugin Manager. (The setting to change in kritarc would be [python] enable_imagine_board=true , to false.) When you copied your resource folder, you also copied your plugins. They’re in the pykrita subfolder.