The path /snap/mame/1122/mame seems a little strange. Is that really the path to your mame executable?
The leading "/" means that "snap" is in your system's root directory, which I doubt. If "snap" is in your home directory, this should work:
Executable: $HOME/snap/mame/1122/mame
$HOME is an environmental variable that contains the path to the current user's home directory.
For comparison, here's the resp. part of my $HOME/.attract/emulators/mame.cfg:
executable $HOME/bin/mame64
args -video bgfx [name]
workdir $HOME/mame
rompath $HOME/mame/roms
romext .zip;.7z;<DIR>
system Arcade
However, I'm still using Attract Mode 2.2.1-50, and I don't know if it's configuration differs from the current version.