There’re certain circumstances that one may accidentally remove truenas apt package when doing apt commands on TrueNAS Scale, for example, updating docker, or updating nvidia drivers. (Although using apt is not recommended on TrueNAS Scale)
Once you remove the truenas package, you’ll find some major function will vanish, and it seems there’s no way to revert unless you do a full reinstallation.
Last week I went into this situation, and with luck I find a way to revert this. I can’t confirm this is really a full revert, but it brings back everything to work as before. At least you can use truenas UI to do a backup.
In short: You can add a apt source that points to ixsystem’s cdn that hosts truenas packages. For instance, I was using truenas (20230704132244~truenas+1) and by searching 20230704132244~truenas on Google, the first result points to that cdn link.
Navigate to parent directory, you got a valid apt source. Simply add this line to your sources.list and apt install truenas. (Make sure the version match exactly.)
deb [trusted=yes] http://download.truenas.com/TrueNAS-SCALE-Bluefin/22.12.3.2/packages/ ./
Hope this can help you some day 