Connect DBeaver to PostgreSQL 13
Changing authentication to md5 in pg_hba.conf won't help you if the password hash is already in the scram format.  You need to set password_encryption TO md5 and then change your password (possibly back to the same thing it already is) to get the password stored in the md5 format.

JDBC which doesn't seem to be maintained anymore

JDBC is maintained.  Perhaps you can't figure out how to upgrade it, but that is a different problem than it not being maintained.
SCRAM does work with JDBC starting in version 42.2.1 (current version is 42.2.18)