@alessandro(Here is a copy of my reply in another instance.)
Looks like the growth comes mostly from Windows (-0.56%) users switching to Linux (+0.52%). MacOS (+0.05%) users mostly seem just to upgrade MacOS and are mostly unaffected by the overall numbers. Inside of the Windows numbers, Windows 10 (-1.56%) users switching to either Windows 11 (+0.92%) or choosing an alternative platform (-0.56%). Numbers do not add up perfectly, because these statistics are estimation based on asking randomly a fraction of the user base.