Sure. All that stuff has consequences. I also used to run a DNS Adblocker on that machine. So after a power outage, all the lights in the kitchen and livingroom (those are the smart ones) would turn on at full brighness (their default state). The internet wouldn't ever come back since it's missing its DNS server. Obviously I can't get any notification of the incident, since my server is down... And I fall back to being reachable via phone or SMS. If my wife tells me via chat or email... That's down, too.
I'm still working on a better solution. It ain't easy, though. It's certainly easier to use some cloud services and have other people keep the infrastructure running in some datacenters which have more redundancy... We have light switches, though. All my smart home stuff is just retrofitted. So we can still turn it off or on with the wall switches. I won't change that until I come up with a solution to this problem. Until then, I've dialed things a bit back and I refrain from making everything "smart" when I can't do it 100% reliably.
And it's just some lights and the washing machine. While I am a nerd and tinkerer, I don't see any good reason to own a smart toaster, fridge or Alexa. YMMV, of course.
Entirely depends on the usecase. If it's a NAS and you only watch a few movies in the evening: Turn it off.
I bult a fairly power-efficient server. Consumes less than 20W and spins down the harddisks if not in use.
I can't turn it off because none of the lightbulbs in the house would turn on anymore, my website would go down, my Fediverse instance wouldn't pull any posts from American people who are awake during parts of the night. My emails and chat messages wouldn't get delivered.
I don't have a UPS. Also depends on the circumstances. I use ext4 as a filesystem which is kind of robust enough to handle power outages. And they're rare where I live. A UPS would draw additional power and cost money. It's not worth it for me at home.