Are there cheap AND good rackmountable UPS units out there? Any recs? 

I don’t need much but would feel better knowing my NAS & UniFi devices are protected.

Working toward a more self-sovereign, creative, kind internet. Husband. Dad. ❤️ startups, games, internet culture, ‘puters, death metal. FC OG | FID442

I too am in the market for what you're describing for my little 12U! 🙂

fwiw, I see enough negative reviews about APC that it's kept me from going that route.

From other nerd circles around the web, I've been told that Eaton makes good stuff, but I haven't ultimately pulled the trigger on anything yet.

If you got a nice UniFi setup, what’s another $1000 to get a good APC UPS to protect that investment? Those UniFi devices themselves deserve the best protection = paying for a good UPS

You can find refurbished APC rack UPS's for quite cheap (~$500) that will protect your entire stack. That's what I've done instead of buying new desktop UPS's and I don't regret it.