Seeking comments on UPSes

I’ve noticed odd power outages that are becoming more and more common around my neighbourhood, and I’m renting my place, so I started looking at maybe getting a UPS (Uninterrupted Power Supply, not the courier company). I know it’s not particularly part of a PC, but I’m trying to use it to better safeguard my machines against sudden power outages.

Anything worth knowing or keeping in mind while I look? Recommendations are welcomed too. Thanks!

Edit: Thank you all so far for your replies. Am adding to the bottom of the post to add a bit of context to try narrow down the scope a little bit.

I’m trying to build my first NAS, with spinning drives, and would love to be able to power down the NAS gracefully in the event of an extended power out (like, more than 30s?). I have some backup solution for important stuff, but would hate to lose the videos and music files that I have.