All right I think I have a solution:
This comes from the database creating one table with one collation and the other with another. In some sites there’s a difference between the databases created during install and when Concrete adds tables during an upgrade later.
The fix is to make the OAuth2ClientScopes and OAuth2Client databases tables have the same collation. If they don’t you can use a command like
ALTER TABLE OAuth2ClientScopes CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;
to fix one or both of them.
Let me know if that does the trick.