I have the exact same problem! Running debian 12 vm for Docker but unable to mount and/or access the 9p-connected shares from the debian-guest.
It's sole purpose is to serve as a single solution consisting of a few different dockers. And i would like to not connect to my shares via smb/nfs.
PS: Do i need to do anything additional to my plain debian-installed vm in regards to guest-tools? Like on win you need to install the guest-tools.exe, but i believe linux already comes with all this built-in?