I can access the home page normally and the administration menu, but when I go to the settings menu, everything appears like this, black
Do you have the animated avatars plugin enabled on your site by chance? If so, try disabling it and rebuilding.
Have you tried safe mode yet?
By deactivating all unofficial plugins I can access the settings, but what now? How do I know which plugin is causing this? Will I have to deactivate one by one? Or is there another way?
It’s likely the animated avatars plugin (assuming it’s installed on your site). Try commenting out of your app.yml, and then rebuild without it.
Is there any way to know which plugin is causing problems?
If you look at the browser console, you might have a clue, based on the error. (F12).