Comment by Arnavion

I use sway and I think it supports security-context-v1, though I haven't tried it. That said, my current setup is just to run cage + xwayland inside the container which gives decent enough sandboxing AFAIK. (I used to use Xephyr but the cage approach gives me dynamically resizable windows). At the very least the host clipboard is not shared with the sandboxed process, which is the primary thing I'm concerned about.