I have googeled and tried more than one solution but none seems to work.
I have edited apparmour, added mp0 to the lxc config, fiddling with other things inside lxc 100.cfg.
None seems to do what I want. Can it be that hard to mount an nfs inside an lxc container?
Got a container running Centos7.
Came across your question. I have Jellyfin in a lxc container on Ubuntu, so not strictly Proxmox, but I don't see why it wouldn't work. My Video files are on a separate drive and I just need Jellyfin to read and play them. The following command line on the host Ubuntu 20.04 allows that:
lxc config device add MrJelly shared_dir disk path=/home/ubuntu/Videos source="/media/gort/black_drive_2/Videos/DVDs"
MrJelly: Is the name of the container for jellyfin
shared_dir: Any made up device name to implement the share
path=/home/ubuntu/Videos: Is a the reference directory for Jellyfin to find videos within the container (default user name being "ubuntu")
source="/media/gort/black_drive_2/Videos/DVDs": The location of the host video files
Works something like a symlink. Not sure if you can change the permissions on the host directory it would allow write access, as I haven't tried it, but it works fine readonly. You can create more than one link. Just change the shared_dir device name parameter and the path=/home/ubuntu/Videos to something different.
Good luck with your project, hope the above helps you out.