The Steam survey has it at 3.6%, although that's obviously skewed towards gamers, and counts Steam Decks in addition to desktops.
You can see that while Windows 10 numbers are going down over the past few months, the Windows 11 numbers aren't making up for it. About 2/3 of that gap are going to Linux with the other third going to Mac. So Mac is getting more market at the expense of Windows as well. There are a significant number of disgruntled Windows users leaving over the past year.
According to Statcounter, Linux's share is 3.86% and rising; but I'd imagine that quite a bit of the almost 16% 'unknown' is also Linux.
https://gs.statcounter.com/os-market-share/desktop/worldwide
Not insignificant at all.