Can you please include the full snap.yaml declaration for these interfaces? It is important that these are named using the usual conventions etc. Also this will show whether you are requesting read or write permission too.
Finally, in this case since eternalmodmanager is not the owner of these paths, this would not normally be granted auto-connect in this case, however you could still check if the user has connect the interface manually (via snapctl is-connected $INTERFACE_NAME) - and if not then prompt them to connect it?
Thanks for the update - I wonder if perhaps the interface name should be a bit more descriptive - perhaps steam-data or similar since then it may convey to the user that the snap is being given access to their complete steam data?
+1 from me for use of but not auto-connect of this personal-files instance for eternalmodmanager. Can other @reviewers please vote? Also if anyone has any suggestions on the name for this interface please feel free to chime in.
+2 votes for, 0 votes against. Granting use (but not auto-connect) of personal-files with write access to $HOME/.var/app/com.valvesoftware.Steam/steamapps/common/DOOMEternal, $HOME/.local/share/Steam/steamapps/common/DOOMEternal and $HOME/.steam/steam/steamapps/common/DOOMEternal. This is now live.
@powerball253 could you please confirm your snap is working as expected. Thanks!