TL;DR: A step-by-step installation of Linux Mint on real hardware and setting it up for typical gaming tasks.
I don't really care much for SOG's other content but his forays into Linux over Windows were incredible for demystifying the operating system to a mainstream audience (i.e. people who watch his content).
Some nitpicks:
- Muta should have used the flatpak version of Steam instead of the system package, the Steam client updates itself (with its own runtime and all) so using a system package over just sharing with flathub is a bit wasteful (it does complicate external storage devices a bit since you have to manually set permissions via flatseal but that's it). (Edit: this is just a small nitpick, the native system package is fine as well).
- There should also have been mention of Bottles over installing Wine as a system package as well as things like the Heroic Games Launcher for GOG and Epic Games titles, Lutris is fine though.
- On long term stable release systems like Linux Mint or Debian, Flathub (or foreign package managers like Nix/Guix) should be your go to for installing software, let the distribution itself manage its core system components which I wish he clarified when he saw Flathub taking multiple GBs on first download.
Other than that, Linux stays winning. 
As you've mentioned in your nitpicks, I HIGHLY recommend advanced users learn to use Nix for packages unavailable in their distro's repos. I have foundational libs and apps from my distro's packages, any proprietary or electron garbage in flatpak (although I use native steam and jetbrains toolbox, bc they work better for me that way), and anything else is through nix-env or nix-shell. There is SO MUCH available through the Nix repos and the tooling is incredible.