Does Request Tracker 4.4.4 works/compatible by Postgres 16?
4.4.4. README says it requires Postgres 9 or later
6.0.2 says it requires Postgres 13 or later
Assuming “or later” can be relied upon for backwards compatibility then it would be worth testing with 16 to see if you see any issues. Likely places where there might be problems would be character handling (utf-8) and sorting behaviour. Other than that RT doesn’t use any Pg only features that I know of, so it’s unlikely to fail entirely.
As always, make sure you have a backup before proceeding!
Good luck.
Simon.