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. 
I see where this is coming from, Valve only supports Ubuntu LTS officially so it would make sense that a native package on those operating systems would work ootb. I've just been using Fedora for so long that me installing flatpak Steam is second nature (instead of jumping through the hoops of installing RPMFusion Nonfree).
Software Manager on Linux Mint is really robust since I've last used it a couple of months ago. I think the impression people have of bad software store guis comes from GNOME software because of how slow Packagekit (the backend) is.
For a while now, Steam on Linux has shipped with the "Steam Runtime," which is a collection of all the dependencies which would be present on Ubuntu. Games targeting Linux for distribution on Steam are compiled against this specific slate of libraries, and this is intended to make them work "everywhere" regardless of which versions are packaged by the distribution. On other distributions (in my experience, ArchLinux and Gentoo) this has worked pretty well. No segmentation faults, ABI problems, or dynamic link errors to report. It can, however, cause weird incompatibilities where something shipped by your distribution works, but doesn't on Steam, or vice versa due to different library versions. The versions shipped by Steam tend to lag behind, but they are also configured specifically for the purpose of gaming.
As far as PackageKit goes, I'd say they hold a very un-enviable position. There are dozens of package managers out there, each with their own APIs, quirks, and functional differences. Trying to apply a one-size-fits-all layer on top of those is a never-ending struggle. Support for Apt and RPM is probably good, but as you start branching out into other systems it going to get rough.