Ikey Doherty of the Solus project posted the following to this Steam issue report:
Alright so long story short, Solus just adopted flatpakIt's an interesting opportunity, using Flatpak makes their packaging more distribution-agnostic, it's obviously more secure than not using any app sandboxing, etc. It will be interesting to see where it leads. This won't be a quick project though as there are some complications around making use of the host's OpenGL library and other factors.
Effectively, we're going to produce a gaming specific runtime that is created with every intention of being entirely ABI compatible for the Steam runtime. The difference being is that it will replace the runtime used by Steam currently.
It will leverage the Solus work on build machinery to provide a highly optimized runtime and SDK, so that Steam can then be provided as a flatpak depending on this repo (Which we'll also set up/host on on the Solus infrastructure).
Due to the isolation from the host, any Linux user will be able to benefit from the runtime, have no ABI issues, and get all the juice out that they need. Additionally, game developers will be able to leverage the SDK for this runtime to build against and test.
Entirely up to the Valve crew if they're interested in this, but it's the direction Solus is going to take and we're open to working with others, and taking orders from Valve on the specification & requirements here. :)
Those not familiar with the Solus Linux project can learn more at Solus-Project.org.