Yep, I have been using Steam on KaOS thanks to flatpak with no major problems.
Thanks to the google cache I've managed to recover my previous posts that went vanished so I'm gonna re share part of those posts below.
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For the unaware, you can install Steam as flatpak by first installing flatpak: https://kaosx.us/docs/flatpak/
Then adding the 'flathub' remote:
$ sudo flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
And finally installing Steam:
$ sudo flatpak install flathub com.valvesoftware.Steam
To run it, just:
$ flatpak run com.valvesoftware.Steam
Wiki/Tested games: https://github.com/flathub/com.valvesoftware.Steam/wiki/Tested-Games
Updates arrived to flatpak and Steam, (...). Below is the list of the games I have installed and played, with the mandatory screenshots:
Bit Blaster XL
Left 4 Dead 2
Pillars of Eternity
This is on my PC at work with an intel i5 6600 and no dGPU, still the performance is great and all the games are more than playable.