The Steam survey has it at 3.6%, although that's obviously skewed towards gamers, and counts Steam Decks in addition to desktops.
https://gs.statcounter.com/os-market-share/desktop/worldwide
Not insignificant at all.
Again, not huge numbers but also not insignificant. But they are quickly growing and taking share from Microsoft. If we look back at (Dec) 2021 the numbers are 1.8% and 2.2% respectively. Those gains are meaningful.