I wrote a guide on how to run GPU-accelerated GUI apps in LXD containers,

The result is that it allows to run Linux apps with full GPU acceleration on our desktop, and those apps are confined in LXD containers.

Currently, the guide uses our current X11 session to send the output.

I have tried this with Steam and it works great. As a side benefit, you can have multiple Steam accounts, then pick and choose which one to start with a simple click.

If you have questions, I am happy to help out here.