In statcounter (https://gs.statcounter.com/os-market-share), there are a number of 'unknown' devices that can reach pretty high proportions. It's about 10% if selecting only desktop OSes. I guess they remove crawlers, otherwise the percentage would presumably have started to go up before 2018 (cursory check, I may have missed something). Also presumably, India wouldn't show a >25% unknown devices for desktop OSes.

So... what are the unknown devices? There aren't 10% (or 25% in India) of people using intentionally obfuscated OSes, are there? Even if it were something like Brave browser hiding your OS, would it reach such a high percentage?