Yeah after doing a bunch of testing what I settled on was a used ThinkCentre Tiny with a dual 10G NIC running OpenWRT, and then a cheap Chinese PoE switch with 4x2.5G ports and 2x10G SFP+ ports. Router and my main computer on 10G, NAS and Wi-Fi (UniFi AP that I’ve had since before) on 2.5G, and then everything else is on a separate 1G switch.
For a home network, 2.5G LAN is really the sweet spot. The hardware is affordable now, the spinny drives in my NAS can’t realistically do more than 200 MB/s for a real workload, there are no single-stream downloads online that are going to be faster (the fastest “normal” download I’ve seen is 2Gbit from Microsoft)
There isn’t a standard that is broadly-adopted, but NUT (https://networkupstools.org/) has reverse-engineered drivers for nearly every UPS out there, usually each brand has their standard so as long as the brand is supported it will work. (NUT is also what TrueNAS, Synology, QNAP, etc use internally for their UPS support)
I’ve had good luck with using NUT with APC UPSes (both consumer models and buying used enterprise rack-mount models).
One cool thing you can do with NUT is share the UPS state over the network, so that multiple machines can respond to the power state instead of just the machine that is plugged in via USB directly.