I’ve also had this issue with libdrm mounting (the same questions were here Core22 gnome extension: mount binding - #3 by yvs and there Apps from snap cannot access /usr/share/libdrm/amdgpu.ids)
It’s not resolved probably because of this still opened bug Bug #2034056 “gnome-boxes/darktable bind mount issue” : Bugs : snapd
on ffmpeg way of mounting:
Perhpaps https://github.com/snapcrafters/ffmpeg/blob/2fa32101cfed656dcf8f61456c91feddf5be5105/snap/snapcraft.yaml#L27 example may help?
that solution isn’t compatible with gnome extension which mounts libdrm too:
layout:
...
/usr/share/libdrm:
bind: $SNAP/gnome-platform/usr/share/libdrm
resulted in (for the following mount):
“Cannot pack snap: error: cannot validate snap: layout “/usr/share/libdrm/amdgpu.ids” underneath prior layout item “/usr/share/libdrm”
Failed to execute pack in instance.”
p.s. only way to get rid of that message (me known) is to disconnect opengl from a corresponding snap. It’s okay if opengl isn’t used there, otherwise not.