Can confirm deleting the deployment and cleaning up the folders did solve that password authentication issue for me.
To do so you need to log into the truenas webui -> datasets -> delete.
Once everything cleaned, you can try to re-install the app through hexos deck. For me it solved the issues mentioned above.
However, i then came across the following issue: Failed to create upload/encoded-video/.immich: Error: EACCES: permission denied, open 'upload/encoded-video/.immich'
After quite some digging in truenas forums the solution to this seems to be to manually create those files in all the directories immich needs:
https://github.com/immich-app/immich/discussions/12798#discussioncomment-12012348
I tried this multiple times, played around with permissions to no avail. Always running into that same issue. I'll be the 1st to admit my linux permissions skill level is straight shit tier.
Will mention it took some time for me to figure out the 'upload/*' folders are the docker named folders as you wont find an upload folder anywhere only an 'uploads' folder mind the 's'. From my fresh installs they all seem properly bound to folders under Application/ or Photos/ (sibling to Application)
Also, if you have data in immich, make sure to make backups / move data around prior to attempting any of this. I don't have any data in mine so went at it with nothing to lose.
Ran out of will to play more with this today. So far, all my folders are root owned + 770 permissions from the default install from hexos. The folders seem to line up in docker as mentioned before regarding upload/* folders.
Just saw in the truenas webui under app->immich, the application metadata stating username immich and a description stating that it runs as non-root user. Might be a problem to look into.
