I don't know to much about security, its all just a hobby for me but maybe it could help you.
As far as I know, basically only open Ports are potential security risks. \
So I would
- close everything down besides 443 80 and 22,
- disable password based login for ssh
- use the snap version since it self updates(I don’t know when the alternatives update)
- Us a “Server” OS/ LTS
I personally use OpenSuse Leap with yast2 online_update_configuration configured to update patch one a week, but you can do this in every distro with cron jobs.