Why not just run a FOSS OS?

A fair question, I actually did install two different Linux distributions a couple weeks ago. For some background I'm a software developer, and consider myself reasonably competent in using Linux.

I started with Fedora. Installed, seemed nice. Then I did a dnf update or something like that. It froze for 4 hours in the middle of the install. So I hit ctrl+z. When I restarted my computer GRUB was attempting to boot an OS version that did not exist and I had to manually try to figure out how to fix this which I was in no mood to do after having the OS for 10 minutes. Also apparently the newest version of Fedora didn't have the concept of turning off auto lock? Or a timer. I'm not sure, but the end result was that if I tried to watch a movie for more than 10 minutes my desktop would helpfully lock, continuing to play the movie.

So I then installed Ubuntu, which was fairly straightforward. Then deleted the couple of things that felt like advertisements (like a direct link to Amazon on the quickbar or whatever it is). Overall, was a pretty good experience until I installed the proprietary Nvidia drivers. Then for some reasons movies (DRM-free files) would stutter. At that point I was thinking about doing some C# development in visual studio anyway so I looked into dual boot installing windows 10 while having Ubuntu installed, and while there are a million articles on how to install Ubuntu with Windows 10 already installed, the reverse did not seem to be true. So I just wiped my system drive and reinstalled Windows 10, which helpfully activated based on my hardware profile even though I'd neglected to save the key.

Installing Windows first is just the recommended way to set up dual-boot, since the Windows installer will always overwrite the bootloader without asking any questions. I think these days there's an automated repair tool on the Ubuntu install media that'll take care of fixing it, though. And with Nvidia drivers it's usually a good idea to install the latest ones from the "graphics-drivers" repository (there should be plenty of guides for that too).

Also, depending on what kind of C# development you do, VS Code can be very nice. DotNET Core is very straightforward to work with, and targeting the full frameworks with Mono is doable with a little bit of tweaking. If it's Unity, then the debugger plugin will be completely useless on Linux, and you'll have to use the very latest beta version of the editor.

If you ever feel like trying Linux again, perhaps try Manjaro? It's a good place to start for a new user, and more polished and stable than Ubuntu and Fedora by far.

Hardware support of laptops for FOSS is not that good unless you restrict yourself to Dell or IBM.

It hasn't been the case since a long time really. I have used it on enterprise HP and Lenovo laptops and everything works flawlessly.

A strange argument: hardware support of laptops for MacOS is officially non-existent unless you restrict yourself to Apple. As soon as you're willing to consider 'Hackintosh' installations you should also consider Linux distributions as those are generally far easier to install and maintain.

While I would say that throwing linux on any random laptop and expecting perfect compatibility is foolhardy, it's really not that difficult to find a linux compatible laptop these days.

In general if you stay away from anything too esoteric, and avoid hardware that needs proprietary drivers (e.g. nvidia graphics, broadcom wifi etc...) most things should work out of the box, but it's a good idea to do a bit of research on anything you're thinking of buying if linux compatibility is desired.

There are also various smaller vendors like system76 that sell laptops with linux pre-installed.

Also has very good support on Lenovo (in my experience), which would make 3 of the largest PC/Laptop manufacturers in the world that has good linux support.

Here is a list of certified vendors for Ubuntu: https://certification.ubuntu.com/desktop/

IBM no longer makes desktop PC s or laptops. Sold the designs to Lenovo years ago.

I had HP and Compaq laptops that ran Linux as well.

That was true 5-10 years ago, these days it's much better (except for some old offenders like Nvidia GPUs or Broadcom WiFi modules). My Asus notebook never lacked any support even though I bought it just three days after that particular model was first released.

My HP laptops have also had zero problems running Linux for years.

Not OP, but for me the only hurdle left is gaming compatibility.