OK, here's what I could figure out for now.
1. All the my-small.cnf, my-medium.cnf, ... files in /etc/mysql have gone. Apparently there's no replacement for these. Correct me if I'm wrong.
2. Everything else seems to work as before.
3. When I log in to the database monitor using mysql -u root -p, I get the following console:
If I understand this right, MariaDB shows me the currently selected database.
4. Any other surprises to be expected?