I've worked in all sizes of companies, in various industries and 3 different European countries.

In my experience it very much depends on the industry the company in, the division one is working in and the size of the company.

Engineering types in an Engineering/Tech company using Linux isn't at all unusual in smaller and mid-sized companies. Sales types or accounting, definitelly are using Window. Creatives tend to use Macs, mainly because the Adobe suite runs perfectly in it and the hardware is superior to PC hardware - designer types almost literally salivate at things like 4K monitors.

Real startups (so, not mature Tech companies that try and still be startups) will definitelly have their devs running whatever they want, whist for example big financial institutions will have everybody on Windows, except perhaps top-level management if they're quirky and prefer Mac for some reason or other.

Then to this add that the kind of professional who not only prefers Linux but can actually say "bye, bye" if they don't get it is almost certainly be a pretty senior Techie (say, a Senior Designer Developer) and even now those are pretty hard to find for a permanent employment position (you can't replace those with AI or outsourcing, not even close, and in the path to such seniority many devs who keep on progressing eventually step into management instead of staying on the Technical career track) - outside a large company (were the hiring manager doesn't have the pull to make it happen), it a pretty good idea to let them use whatever OS they want in their work machine, even if it has to be with the proviso that they won't be getting any support for it from the IT Support group (which, trust me, they will be fine with).

If a hiring manager has the pull for it and there are no regulatory reasons to make it be otherwise, it's pretty dumb not to let a rare resource like a really senior dev use whatever the fuck they want on their work PC if that's going to allow you hire/keep that person.