See also: https://getsol.us/2024/07/15/dropping-apparmor-kernel-patches/
Dropping snap support significantly reduces the the maintenance burden for kernel maintainers, as they no longer have to deal with syncing up a bunch of patches from Canonical. I don't know if that's the only reason. I doubt it is.
Pure speculation here: it seems to me that snaps have become less popular in the last year or two across many Linux distributions. Flatpak (and to a lesser extent appimage) has more or less won the universal-linux-app-format battle, so removing it from Solus aligns us with broader Linux trends and user expectations. Again, pure speculation.
