Exclusively Ubuntu Linux these days:
- the built-in 10'-ish interface taskbar (originally intended to be a phone OS) works well for my home theater and I use the TV as my desktop monitor also. Used to run mythtv, but haven't bothered upgrading to replacements since I don't use the OTA tuner any longer now that streaming took over.
- also using a desktop version for my networked media file server in the laundry room. Why bother running headless when the desktop doesn't get in the way at all?
- bedroom PC is general purpose
- works with just about any old hardware
- free, comes with built-in word processor/spreadsheet/browser
Disability leaves me with little options because I can't afford to pay for anything extra. I don't buy software any more.
I have an iPad Air2 that I bought to run a Mackie audio mixer while I was still doing that. It gets little use these days, mainly for Zoom calls and linked to my iPhone.
The best thing about Linux is I can get virtually any junk hardware on Freecycle and turn it into a usable PC with basic drivers available, or I can build my own file server RAID and not be stuck into any particular hardware/software configuration.
Also I haven't used any virus or spyware blockers since moving to Linux, and haven't noticed a single issue with only a wireless router protecting it. Hackers aren't interested in attacking my Linux desktop. There aren't enough of us slogging through the pain of Linux in the wealthier northern hemisphere to make it worthwhile trying to hack it. A more likely target is an enterprise Linux network file server/web server/database management system. Far more likely for enterprise to get hit because of the more prolific web connectivity of an enterprise system. A router firewall with all ports blocked is fairly secure. Even when the Linux shell parameter stack pointer bug exposed every Linux to hack (how was that not intentional?), I didn't notice a problem. Nobody cares about hacking your Linux if you aren't rich and kids won't know how to do it with a stupid script.
The worst thing about Linux is the lack of driver support. Particularly vexing is that power management doesn't work on any of my PCs. I imagine if I had a laptop it might work, provided it's a mainstream PC and not an edge case. None of my motherboards wake up properly and the display won't turn back on unless I plug cycle the HDMI (provided the motherboard wakes up at all). I've disabled all the states to keep things from getting lost and still my PCs are not entirely reliable on wakeup. Sound card drivers, DAW drivers, JACK etc. is a nightmare for a casual user without deep OS knowledge and the need to use something else to get rid of Pulse Audio is also problematic because Ubuntu is pretty much the only plug-n-play Linux where you just install it and run with it without having to wrestle with customizations and severe desktop incompatibilities. It's possible to find supported hardware, but it's more expensive and there are very limited choices.
MacOS is okay for people who don't want to think and don't need to do anything fancy. It just works mostly.
Windows is okay for people who need to run lots of software, but watch out...it's not secure.
BSD? Tried FreeBSD once a long time ago. It was cryptic, seemed poorly supported, could barely get it working and it wasn't useful for anything with the GNU support available at the time. Maybe it's better now but I'm too old and tired to look into it.
I'm surprised nobody mentioned virtualization. That seems to me like probably the most complicated but also potentially the most flexible. Windows will get you great hardware support and virtualization will get you great enterprise level Linux/Unix support. With the huge hard disks and fast processors with ginormous RAM it seems like virtualization should be a slam-dunk. I haven't tried it yet, but it seems to me for all you pro enterprise sysops you'd definitely be running virtualized everything under Windows and enjoy the best of both worlds?