/usr/sbin/sshd -T
sshd: no hostkeys available -- exiting.

@sholan do you know a very robust way to detect the port SSHd is using with bare minimum built-in tools? Such detection may cause side-effects if init scripts fail due to parsing errors of config files or VPS provider customize their Ubuntu images. But generally sounds like a good idea, if of course chaning sshd port is a common use-case for our users. So maybe lets wait for other to raise interest.

Maybe this is naïve but:
/usr/sbin/sshd -T | grep "^port " | cut -d" " -f 2
or with awk :
/usr/sbin/sshd -T | grep "^port " | awk '{print $2}'

I am not of any help regarding the constraints, I'd go headlong towar parsing /etc/ssh/sshd_config ... grep Listen

But as you said, drawbacks exist.
netstat might not be present on the system and so on

I'm just raising an idea, I'm far from having all the constraints in mind

Thank you, this is really nice to be part of it, Cloudron is just a dream come true, wish I had heard about it years ago

The idea here is to prevent locking out an admin, while the other topic is to help such admin do the same but after Cloudron installation