DBeaver is the best free (with a paid option) DB client in my experience and I have tried many. I have used it with many databases: DB2 (MVS), DB2(linux), Postgres, ISeries, MySQL and SQLite. Datagrip is better IMO, but I have the JetBrains Ultimate Edition for other reasons so it is "free" to me in a sense.

DBeaver is my go-to as well, came here to ask the same question.