also, a quick tutorial how i set up Jellyfin:
Create a public folder in HexOS
Go to apps in HexOS, go to Jellyfin, and click Install. It will open TrueNAS UI. user is truenas_admin and password is the HexOS password. (If it sends you to TrueNAS dashboard, go back to HexOS, Jellyfin, and click on Install again)
Under Network Configuration check Host Network
Under Additional Storage, click Add, choose Host Path, in Mount Path is how the folder will look in jellyfin, in Host Path find the folder you created in HexOS.
Thats it for the settings, click Install at the bottom
Now in TrueNAS UI go to Datasets, click on the folder created in HexOS, scroll down to Permissions, and click Edit
Click Add Item, Who: Group, Group: apps. (you need to scroll at the end once or twice to be able to see full list, then find apps, should be near the end, its not in alphabetical order). Set permissions like in the picture, then click Save Access Control List. Thats it for folder permissions.
Go to Apps, jellyfin, and click on Web UI. Then from there set up Jellyfin as normal, when u click on +Folders you should be able to see the folder you added in Host Path, /shows in my case.
Thats it, jellyfin should work as normal now, just as if you set it up on your windows machine.