I’ve installed i3wm on top of Silverblue in the past as a proof of concept, but that means you are carrying around all the GNOME stuff at the same time. Yes, you can go in and rpm-ostree override remove a bunch of packages, but that kind get pretty hairy as you try to figure out all the GNOME packages and dependencies required.
Optimally, someone could create an i3wm version of Silverblue, similar to what has been done with KDE/xfce here:
If we can get enough contributors to maintain these kinds of versions of Silverblue, perhaps we can convince the powers that be to start supporting them with proper resources/infrastructure.