I had a very similar issue to this, on Ubuntu, using the slack snap.
I was experimenting with ro bind mounting /etc/resolv.conf from /run/systemd/resolve/stub-resolv.conf instead of symlinking, because I want to prevent any undesired modification to the file by various vpn clients.
However, with the mount in place:
mount -o ro,bind /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf
I got the following error when I tried to launch the snap.
cannot update snap namespace: cannot create writable mimic over "/etc": no such file or directory
snap-update-ns failed with code 1
The snap itself has a few bind mounts from /etc, but nothing about /etc/resolv.conf specifically.
Is this potentially a snapd bug, or something else ?
Cheers, Just