> The sensor library that everyone relies on, lm_sensors, is semi-abandoned and didn't recognize sensors on my relatively popular, 7 year old ATX motherboard

This is mainly because the companies that make the “super io” controller chips (ITE and others) are deluded and think that they have some sort of cutting edge tech and their chip documentation must be super secret.

Years ago there was someone at a mobo manufacturer who would leak the datasheets, but they left or got found out, and there hasn’t really been a source for that info since.