While most people will be using a normal package for Steam on Linux or the Flatpak, Canonical continue pushing their own Snap packages and one that's needed a lot of work is Steam. Giving an overview on some of the work done Canonical's Ashton N wrote a post on the official Discourse Forum to go over some of it.
Since Snap packages aren't like normal packages, like Flatpak they run in a more contained environment which places various limits on what they can do. The idea is to keep your main filesystem safe and untouched but that comes with many problems that need special solutions.
For the Steam Snap, Canonical had to ensure things like Proton would work properly and they say they've "made huge strides in improving the Snap's compatibility in this respect" including allowing external drive mounts, improved NVIDIA driver support, network compatibility, /usr files, and /lib/libexec files. If you have games on other drives this is now supported across /mnt, /media, /run/media, /opt, /src or /home so pretty much anywhere you set up a Steam Library should now work!
The popular MangoHUD is now bundled directly with the Steam Snap too, so you can easily use
mangohud %command% as a launch option on games to get it. GameMode from Feral Interactive has also been bundled too so you can use
gamemoderun %command% just like above which required changes to GameMode itself which has been merged into the project.
Lots more work was done like a significant improvement to controller support, debugging tools and various smaller issues being solved.
Eventually it should work just like the normal Steam package, but have everything it needs in one Snap package that would run across various versions of Ubuntu (and other distros) while having better security for the host system.