If there is docker image for what you need, use docker image.
If not I would recommend systemd-nspawn, it's chroot but can run systemd init, with efforts you can run GUI applications from it too., wiping that is just sudo rm -rf.
Also using PurelyMail, tt's the cheapest non-free email service I can find.
It passes email delivery tests, setup SPF, DKIM and DMARC easily without issue.
The downside is that it's basically one man handling whole this service, but I assume this service has been fully automated because the margin of profit is so low.
I am using ZSH, that function that allows you to type part of the command and then do UP key to find previous command starts with same prefix is killer function for me.
(I don't know if this function is added by oh-my-zsh or not.)
On Ubuntu 22.04 based distro, you can try install HWE (hardware enablement) kernels but you need a phone that can share WIFI/mobile connection through USB cable.
I currently have Pulsed Media seedbox, which has SSH access (no root) and docker, haven't tried something like plex/jelyfin so I can't tell how well it works.
You should google the name if you want to try them, negative things pops up.
Password authentication can't be turned off for SSH.
If there is docker image for what you need, use docker image.
If not I would recommend systemd-nspawn, it's chroot but can run systemd init, with efforts you can run GUI applications from it too., wiping that is just sudo rm -rf.