I believe this is a slightly controversial topic, at least from what I have gathered so far. Some say its best to leave the server on to spare the life time of the spinning rust. Other seem to prefer to save power and boot the server off each night. So wanted to chip in and hear what folks here do and why do what you do.
Bonus question; Do you guys have a UPS? Is it a must have for a homelab, or does it just depend on the usecase?
You can do whatever you want. Don't let anyone tell you it's "wrong". A big part of homelabbing is to try stuff. If it doesn't work, that's fine, you learned something, and that was the point.
For me, I don't see a UPS as essential. It's generally a good idea, but not strictly essential. My servers are on 24/7, because I have services that do things overnight for me. I also know that some people access my lab when I'm not awake, so I just leave it on so it can be ready for anything at any time. It poses some unique challenges sometimes when running stuff that's basically 24/7/365.
I have a 'dumb' UPS for my synology NAS to protect against short power outages - it's done after a minute or 10 though so if I'm not at home it'll crash anyway. In Retrospect I should've gone for a smart one that will shutdown the NAS.