Running GitLab Omnibus Database Service(s) as Non-Root Account

Dear Community,
We are using GitLab Omnibus, which was set up using default values at installation.
A recent security compliance audit pointed out that the database service should not run as root.
We have not managed to find a solution to reconfigure the PostgreSQL service to run as a non-root account. Using Ubuntu 20.04 LTS.
Can someone explain how this can be achieved, what file permissions need to be adjusted etc.?
Thanks very much in advance.