Sorry for the delayed response - I saw what you meant in the v2 manual about the proprietary connector and thought I would just leave it at that, but I had another thought.
It sounds like you do have some access to Windows/L-Connect, have you switched the fan profiles to sync with the MB? This should stick after a shutdown and not need to be re-set, you will lose the ability to create fan curves in L-Connect: https://lemmy.ml/pictrs/image/fac93968-ab47-407b-8e49-91577d8762d9.png
Also, are you connecting the UNI HUB directly to the MB pins, or is it running through a splitter or extender? It looks like the UNI HUB v2 does have a sense pin (the v1 does NOT, that’s the reason for the workaround I have to use); some additional extenders and splitters are missing the sense pin, so even though you can control the fan speed from BIOS, you can’t see the RPMs in BIOS so it might look like it’s not recognized.