I’ve been able to control a consumer-grade CyberPower UPS for just my modem/router via a Raspberry Pi using Box64 to emulate the linux command line software for communicating with the UPS. I’ve never had any issues, and it had pretty okay documentation. You just connect it to a host PC via USB.
https://www.cyberpowersystems.com/product/ups/standby/st625u/
This is the one, nothing special.
As you can see though, source, rpm, and deb versions are available. If a low-power consumer grade one like this has Linux support, I’d daresay most of them do. Like I said, I never had trouble.
You can run it on a Pi via Box64. Source: I did it.