Hi Martin,
At the point I disabled "XHCI Hand-off" I did not have the "above 4G decoding" in mind, so after a reboot only mouse buttons 1 and 2 were working
and the system also seemed a bit "unstable".
Because of this I checked BIOS again and noticed that "above 4G decoding" was enabled, then I disabled it and now mouse are keyboard are fine.
I believe that updating BIOS somehow enabled "above 4G decoding".
Don't really know if "XHCI Hand-off" should be enabled or not, the system works with it enabled and with "above 4G decoding" disabled.
Nice if someone who knows could clarify.
(Tried the link to the BIOS simulator but it won't work with my Firefox installation, anyway I've used it before from a Win10.)
And, yes, I remember reporting this hardware a few years back.