This is expected because some features are not upstream yet, despite years of work towards that.
You can force-enable apparmor by editing interfaces/apparmor/backend.go, look for openSUSE Tumbleweed there.
I have the same list of features as you and my snaps are working fine.
It looks like you don’t have the snap apparmor profile installed. Did you use my overlay/ebuild?
The problem which i have faced, was releated to funtoo openrc.
Funtoo do not have systemd. On gentoo with systemd it works.
the only snaps which do not work as expected, or just not works are chromium-vaapi and anbox.
I only run gentoo with systemd, so I probably cannot be much help to you. Keep us posted on your efforts. Maybe if you come up with an OpenRC ebuild we could combine our ebuilds end submit them to Gentoo/Funtoo official.
Impossible, OpenRC do not provide such capabilities required for snapd.
So i am on gentoo with systemd now.
But i suspect snap in insane performance impact… I could check if i am right, and will report.