I highly doubt the OS is responsible for how BPM is counted.

the apple watch ultra 2 was sometimes 15 bpm faster than on a Polar H10 chest strap

How did the Polar and AWU2 compare before the update? What about previous updates?

Keep in mind with these “fitness trackers” that they’re all relative meaning the exact numbers will never match different devices and products. You have to stick with a single device and take relative measurements. The exact numbers are useless, it’s the trends that you need to pay attention to.

A homeserver is just a component(s) of your homelab…