I’m not sure if I did this correctly, I used chroot from the live USB to the /mnt point of my problematic system.
When I ran systemctl status postgresql.service it said
System has not been booted with systemd as init system (PID 1). Can't operate. Failed to connect to bus: Host is down
When I ran journalctl -xeu postgresql it said (hopefully I am formatting this correctly, I am following this How to provide good information)
-- An ExecStartPre= process belonging to unit postgresql.service has exited.
--
-- The process' exit code is 'exited' and its exit status is 1.
Jun 01 12:40:12 user-pc systemd[1]: postgresql.service: Failed with result 'exit-code'.
-- Subject: Unit failed
-- Defined-By: systemd
-- Support: https://forum.manjaro.org/c/support
--
-- The unit postgresql.service has entered the 'failed' state with result 'exit-code'.
Jun 01 12:40:12 user-pc systemd[1]: Failed to start PostgreSQL database server.
-- Subject: A start job for unit postgresql.service has failed
-- Defined-By: systemd
-- Support: https://forum.manjaro.org/c/support
--
-- A start job for unit postgresql.service has finished with a failure.
--
-- The job identifier is 110 and the job result is failed.
-- Boot 1842fc0692764d3088dafb78c66849f1 --
Jun 01 12:43:46 user-pc systemd[1]: Starting PostgreSQL database server...
-- Subject: A start job for unit postgresql.service has begun execution
-- Defined-By: systemd
-- Support: https://forum.manjaro.org/c/support
--
-- A start job for unit postgresql.service has begun execution.
--
-- The job identifier is 124.
Jun 01 12:43:46 user-pc postgres[852]: An old version of the database format was found.
Jun 01 12:43:46 user-pc postgres[852]: See https://wiki.archlinux.org/index.php/PostgreSQL#Upgrading_PostgreSQL
Jun 01 12:43:46 user-pc systemd[1]: postgresql.service: Control process exited, code=exited, status=1/FAILURE
-- Subject: Unit process exited
-- Defined-By: systemd
-- Support: https://forum.manjaro.org/c/support
--
-- An ExecStartPre= process belonging to unit postgresql.service has exited.
--
-- The process' exit code is 'exited' and its exit status is 1.
Jun 01 12:43:46 user-pc systemd[1]: postgresql.service: Failed with result 'exit-code'.
-- Subject: Unit failed
-- Defined-By: systemd
-- Support: https://forum.manjaro.org/c/support
--
-- The unit postgresql.service has entered the 'failed' state with result 'exit-code'.
Jun 01 12:43:46 user-pc systemd[1]: Failed to start PostgreSQL database server.
-- Subject: A start job for unit postgresql.service has failed
-- Defined-By: systemd
-- Support: https://forum.manjaro.org/c/support
--
-- A start job for unit postgresql.service has finished with a failure.
--
-- The job identifier is 124 and the job result is failed.
When I looked at that PostgreSQL support page I ran the code to see the version and it returned 12.