I changed (utf8mb4_general_ci), but it automatically reverted to (utf8mb4_unicode_ci) so still the same problem (this appeared during the Joomla 3 update to Joomla 4). The problem only concerns "Advanced Module Manager" there is no problem on the other Regular Labs extensions, they all update correctly without error messages
I see that Joomla uses utf8mb4_unicode_ci by default. So change everything to that.
And you might have some table fields set specifically to a different collation.