This issue is going to be fixed with the edge ISO and Mint is way more similar to Windows in terms of UI that helps a lot of beginners to transition smoothly
Probably depends how you define things. Like, is Xubuntu Xubuntu or Ubuntu with Xfce included by default? How much change is necessary before it's not "debian with added bits"?
Probably based on how the OS defined itself. Steam is able to gather information like this easily.
Hannah Montana Linux is probably the most popular Linux distro.
In all seriousness, popularity isn't necessarily the best metric for what you should run on your computer. Ubuntu might be fairly popular, but it also isn't particularly good.
Ubuntu 100%, if you count how many distros are ubuntu based (and collaterally debian based), but I believe it is the most used one even if you only count official ubuntu releases
Maybe arch would be quite high, if you count the steamdeck as desktop (maybe), and the big increase on arch users in the past couple of years (wen't from being rare to 1 in 3 users saying "I use arch btw")
Thst depends in a lot of things.
What do you mean with "PC"? Is a smartphone a PC? Is a steamdeck a PC? The Laptop of a government employee? A Raspberry Pi? What about a TV-box or an e-reader?
Because if you mean in general on non-server hardware it's probably some weird Chinese/indian fork for their government PCs.
Otherwise it could be Arch due to the steam decks, but then again it depends on how tightly you define "distribution". As others have mentioned, is Xubuntu their own distribution or does it count as Ubuntu? What is Mint/Pop!_OS?
But no matter what, it's not MX Linux.
PC is a computer based on IBM PC compatible standard, so usually x86 processor architecture with compatible with it components.
The term is so common that in practical language people started to use it as a replacement of the "desktop PC" or overall anything that is not pocketable or Apple.
But I guess with such question from OP it does not matter, as computers at the edge of the definition (like x86 Android tablets) are in a fraction of percent and won't matter in "what's the most popular".
I would say we're beyond the era of PC referencing the classic "x86 IBM Personal Computer compatible" definition. PC could reasonably be considered to include many ARM systems, considering there are now Windows laptops shipping with ARM processors that can run "PC" software. Besides, most new x86 PCs aren't IBM PC compatible anyways as legacy BIOS support has been dropped by a lot of UEFI implementations. I would consider any device that runs a desktop style OS (be it Windows, Linux, or even MacOS) a PC. The distinction in my mind is specifically mobile vs. desktop. Android and iOS are not PC. They're primarily touch driven and apps are restricted to a certain format with a centralized app store where you are expected to get all of your apps. Windows/Linux/MacOS are primarily keyboard and mouse driven and you have a lot more flexibility on acquiring new apps, with their forms of "sideloading" and "rooting/jailbreaking" being things that are just normal and accepted rather than workarounds/hacks to break out of the walled garden. I would also go as far as saying a smartphone can be a PC if you have a PC like OS on it, such as mobile Linux OSes that let you run desktop applications.
define "most popular" please
for instance https://distrowatch.com/dwres.php?resource=popularity, does that metric fit your definition?
Anyway whatever the answer it doesn't really matters, at the end of the day it is always Linux anyway, regardless of package manager, desktop environment or init.
I'd just warn you against Ubuntu, because its company Canonical is behaving a lot like a young Microsoft these days.
