We see the nearly 33-year-old OS’s market share growing 31.3 percent from June 2023, when we last reported on Linux market share, to February. Since June, Linux usage has mostly increased gradually. Overall, there’s been a big leap in usage compared to five years ago. In February 2019, Linux was reportedly on 1.58 percent of desktops globally.
A quick google search will probably turn up lots of discussion forum results where Linux users were talking about the best way to change their user agent and complaining about sites that forced them to during ~ late 90s -> 2015 (give or take - prob was pretty rare by then).
In most cases it wasn’t anti-linux, it was the site being programmed to go “the user agent has to match these things or tell the user it’s not compatible with their browser” - but in MANY cases if Windows (or presumably MacOS) wasn’t one of the matched things, you received that message. Off the top of my head I specifically remember having to change it to pay my cable bill and get to my bank website.
There were also some more subtle cases where the site would load but some shit would not work (most famously the web interface for Office365 when it was newish).
So you can doubt, but this is what it was like to run Linux in the 2000s.
More recently (for sure post 2016) I recall having to change it to get the Netflix website to let me play content or fix some other bit of functionality on their site. As of today I haven’t run netflix in a browser window in years, but I assume that’s been resolved by now.