What are corporate users using?
Windows on PCs, Linux is used mostly only on servers (RedHat/SuSe), hardware brands are usually HP, Dell and Lenovo.
I think that is my standard
Why? Do you expect companies to ask you to use your own PC for work instead of providing the tools you need? Be wary of those who do, using whatever personal PC for company work can lead to data breaches and that's a very serious problem.
World of Warcraft has its own anticheat that works on Linux no problem, if Blizzard can do it why Riot can't? It's not that WoW has more players than LOL so it could be justified, it's actually the opposite.
If I use ubuntu I’m somehow forced to use them.
Yes, that's why I stopped using it years ago (among other reasons).
Users are not out of options, they don't need to check the origin of the apps themselves, it's enough to ask other users what distros don't do the things they don't like and use those.
The solution is using a distro that has support for containers (flatpaks preferably) but doesn't force them on you, so far I haven't found a single use case in which they're truly needed on desktop so apt update still does everything for me.
There's some software that I compile myself (emulators), it cannot be upgraded with a packet manager but that has always been the case.
I use Linux MX but there are other distros with the same approach. It also makes it really easy to see if you're installing them because flatpak is a separated repository from non-container apps (I think it's also updated by the package manager but I haven't tried so far).
Yes I was referring to snaps.
distribution hopping will add lots of unnecessary frustration for me.
That's a fair point. Cinnamon is the desktop manager and it's been the only one available on LMDE so far, in any case, it's perfectly fine to use Mint, just know that if they ever decide to make LMDE their primary, you have nothing to worry about, being already used to Cinnamon we'll make it so you won't notice the difference at all, LMDE is still Mint after all.
It's been a while since I installed Debian directly, anyway I believe it's a godsend as a base and amazing as a server, but for desktop usage I prefer derivatives because I find them more user friendly.
LMDE vs MX: they're both really good, MX is a bit more "nerdy", LMDE is beautiful out of the box and has the total friendliness of Mint, MX (XFCE) is a little more barebones when it comes to user apps/GUIs but it has some fantastic tools to get into its customization, more flexible than LMDE from that point of view.
Ubuntu is based on Debian. LMDE have existed as a backup plan in case something wrong happened to Ubuntu, Mint could still go on without problems.
Using LMDE is like just removing a "middle-man": Debian --> Ubuntu --> Mint, Debian --> LMDE. (I've been using LMDE for a few years on my notebook while on my gaming desktop I use Linux MX, also based directly on Debian).
I understand some people don't want Ubuntu to avoid commercial distributions but for me the reasons are different.
Ubuntu LTS is base on the testing branch of Debian, while non-LTS are based on Debian sid, that is the development branch, in both cases you lose - in my opinion - one of the biggest advantages of using Debian that is rock-solid stability, sid packages are not controlled by Debian security team so in that case you also lose out on security.
Another reason is Ubuntu have been trying to push their own sort of "proprietary" version of containers that have been proven times and again to have serious security flaws. They also use them everywhere and I don't like that, I want to be free to decide if/when to use them, not being forced to do so for everything.
Sometimes they make very questionable decisions, like when they wanted to discontinue libraries for 32bit compatibility (while Debian does not), ignoring there's still a huge amount of 32bit software that cannot be recompiled to 64bit (mostly Windows games), that made me question they know what they're doing.
I think you would get more suitable recommendations if you told us what your use cases are. Did someone else give you those requirements? Are you new to Linux?
Arch, Slackware current (KDE), Suse tumbleweed, Debian sid and Fedora tick all the boxes but I wouldn't recommend Arch nor Slackware to someone who never used Linux before, nor I would recommend Debian sid for desktop usage (unless you know what you're doing) because its packages are not controlled by their security team.
Free and open-source. Receives regular software and kernel updates.
All of them (desktop). The difference in updates is between a rolling release or non-rolling one.
Rolling means they receive updates to software and kernels continuously as soon as they are released, you always have the latest versions but that could lead to instabilities, non-rolling (or stable) are updated less frequently so are more stable, which one to choose depends on what you need to do with it.
Avoids X11.
Fedora, Suse, Ubuntu, Slackware current, Debian, Arch, if you choose GNOME or KDE you'll have Wayland as default AFAIK, probably others.
Supports full-disk encryption during installation. Doesn’t freeze regular releases for more than 1 year.
All of the above.
We recommend against “Long Term Support” or “stable” distro releases for desktop usage.
LTS is a version, not a distro. Distros that offer LTS versions also have a non-LTS ones, get those and you're fine. Tho not wanting a stable is weird, they can be the best for desktop usage depending on what you need to do.
Supports a wide variety of hardware.
That depends on the kernel, all kernels support a wide variety of hardware, non-LTS versions are best for more modern hardware.
Preference towards larger projects.
All distros mentioned are large projects, Debian is probably the biggest, it also supports several different architectures.
Being verified on Steam Desk is my parameter for deciding if I'll consider a game or not, even if I don't have a Steam Deck (yet). I'm perfectly fine with that, not asking for a Linux native version as long as the game works as it should on Proton.
Do I basically just start off installing one distro on the full hard drive and then when I go to install the others, just choose the “run alongside” option? or would I have to manually partition things out?
If you install one distro on full hard drive you won't have room anymore for the rest, if you want multiple operating systems on your machine you need to partition manually with some planning ahead on how to allocate the space.
Any thing to worry about with conflicts between different types of distros
They don't interfere with each other, they don't even "see" each other once you booted into one, they only share the boot manager.
That being said, what you intend to do was the only way to learn many years ago when computers weren't as powerful as they are today (I did learn that way), but today ANY PC can manage virtual machines, they are much more practical and can save you a lot of time when you mess things up, because whatever you do is confined within the VM and doesn't affect your PC as a whole.
Install Virtualbox, have a look at how it works and use that to do all experiments you want, you can even learn to multiboot inside a single VM, without the risk of messing up your system.
True, it's the desktop manager that can make a difference but you can install any DE on any distro.