Linux

Try Bazzite:

https://bazzite.gg/

It will give you an experience that's familiar compared to the Steam Deck, and everything will "just work" out of the box.

It already has Steam installed and is a great desktop for general use.

I really like fedora out of the box but if you’re used to windows some will recommend Linux mint. In fedora there are a lot of packages installable via the software store as well as downloading app images and RPM files.

1. The various versions or flavors of Linux are called "distributions" or "distros." There are several that are intended to be ready to go out of the box. Linux Mint is a pretty good one for general desktop use though they're kinda behind the times with Wayland and such. I see a lot of folks recommend Bazzite but I personally know nothing about it. I'm using Fedora KDE, Fedora is meh, KDE is pretty good.

2. If you're building a gaming desktop specifically for Linux, I recommend going with AMD GPU and an Intel wi-fi adapter. There are some Wi-Fi adapters that don't play nice with Linux but Intel's drivers are pretty good. AMD releases their drivers right into the kernel, there's nothing you need to do at all to get AMD GPUs working on Linux, Nvidia is a bit more of a pain. Also, with desktop peripherals, avoid anything that needs one of those configuration utilities, they tend not to be available for Linux. I use a Coolermaster MasterKeys Pro M keyboard which all configuration happens on the board, they don't offer any software for it. Highly recommended.

Oh also: Asrock's RGB lighting weird and non-standard. If you want to use open source stuff to control your RGB lighting and that's important to you, I recommend against Asrock. Just so happens my build's RGB is controlled via a controller built into my case.

is there a Linux… idk what to call it, type? OS? Thing??? that runs out of the box without me having to install additional software manually or at least automatic setup wizards

The word you are looking for is called a distribution, or distro for short.

I'm surprised no one else has mentioned Bazzite, which should be exactly what you're looking for.

is there any specific hardware that works easier with Linux

An AMD GPU for sure. Nvidia drivers have come a long way, but they don't generally behave as well out of the box like AMD.

Pro tip is to install a virtual machine like virtualbox or something on your Windows system. They're super easy to set up with loads of tutorials on youtube.

From there you can install any number of linux distros (I recommend Mint or Pop!) and try them out without having to commit to real hardware. I would put the VM in fullscreen and pretend it was a real system, and use it as my dedicated machine for as long as possible. You can even install steam to get a feel of the setup process (bear in mind you'll need to set up stuff for graphics acceleration to play most games but the basic setup should be fine!)

As for setup. Most Linux distros are as easy to set up as Windows or MacOS: USB in, boot, select a few basic options and stick to defaults. Reboot. Install stuff. You don't even need to deal with drivers (even Nvidia is cared for by most installers) which was nicer than burrowing through NV/AMD's websites to get their driver installers set up.

At that point you won't be wondering if youve made the right choice when it comes to your next build, and you can get right down to actually using your PC instead of googling things. Good luck!

You can just buy a system with Linux preinstalled. My laptop is from System76. I usually build desktops/towers from scratch but they sell those too.

Installing apps has always been easier on Linux then on Windows as Linux has had large free app stores back 30 years. The question is more are the apps you want in the app store. If not things get harder. I like Debian based distros like Ubuntu or Linux Mint as they have large app stores.

You might want to look at distrowatch.com. Mint is currently at the top.

I also recommend Linux Mint. It's been hands down the best experience of all the Linux distros I've tried.

The installation is done with a USB stick. In short, you download the Linux iso image and create a bootable USB stick with a software. In Windows I have always used Rufus for that.

The Linux installer gives you a choise to wipe everything and install Linux. Installing Mint has always been very straight forward.

I can't comment on hardware since I've only used Linux on +5 year old laptops. They seem to work fine.

There most likely will be many new things that can feel confusing in the beginning, but I'm sure you'll get the hang of it. There also are tons of good tutorials of everything.

Best of luck to your Linux project!