What about the default files app (com.android.documentsui)? I think we can all agree that it's so ugly that even the stock OS disables it. Technically the stock OS doesn't completely disable it, but it does hide it from the user and you can't even open it from settings.
Could we do the same thing and use something like Material Files as the user-facing file manager? There are a few problems with Material Files though, so a different app might have to be selected.
- The license is GPLv3
- Root access is supported through the file manager, so that would either have to be disabled or set to view only.