There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another theory which states that this has already happened.

"Far out in the uncharted backwaters of the unfashionable end of the Western spiral arm of the galaxy lies a small unregarded yellow sun. Orbiting this, at a distance of roughly ninety million miles is an utterly insignificant little blue-green planet, whose ape descended life forms are so amazingly primitive that they still think digital watches are a pretty neat idea. This planet has, or had, a problem, which was this. Most of the people living on it were unhappy for pretty much of the time. Many solutions were suggested for this problem, but most of these were largely concerned with the movements of small, green pieces of paper, which is odd, because on the whole, it wasn't the small, green pieces of paper which were unhappy. And so the problem remained, and lots of the people were mean, and most of them were miserable, even the ones with digital watches. Many were increasingly of the opinion that they'd all made a big mistake coming down from the trees in the first place, and some said that even the trees had been a bad move, and that no-one should ever have left the oceans."

Are you seriously suggesting running a Plex server on the Steam Deck in addition to the Plex media player? Because last I checked, the Plex media player can play (I think) but not index them. I'm a happy Plex user with lifetime Plex pass, but that's just stupid.

Kodi is a solid standalone solution for exactly what OP is asking, with controller support. Kodi wouldn't be my first choice for networked media playback, but it's brilliant for exactly OP's use case. And it really isn't laggy unless you overload it with plugins.

OP is talking about local content! Attached to the dock. Plex App is not the right solution for that. Kodi is probably their best choice.

Unraid 6.12 and higher has full support for ZFS pools. You can even use ZFS in the Unraid Array itself - allowing you to use many, but not all, of ZFS extended features. Self healing isn’t one of those features, though, it would be incompatible with Unraid’s parity approach to data integrity.

I just changed my cache pool from BTRFS to ZFS with Raid 1 and encryption, it was a breeze.

I generally recommend TrueNAS for projects where speed and security are more important than anything else and Unraid where (hard- and software-)flexibility, power efficiency, ease of use and a very extensive and healthy ecosystem are more pressing concerns.

Unraid is also awesome for places with high energy cost: Unlike with your typical RAID / standard NAS, it allows you to spin down all drives that aren’t in active use at a relatively minor write speed performance penalty.

That’s pretty ideal for your typical Plex-server where most data is static.

I built a 10HDD + 2SSD Unraid Server that idles at well below 30W and I could have even lowered that further had I been more selective about certain hardware. In a medium to high energy cost country, Unraid’s license cost is compensated by energy savings within a year or two.

Mixing & matching older drives means even more savings.

Simple array extension, single or dual parity, powerful cache pool tools and easily the best plugin and docker app store make it just such a cool tool.

Plex supports native auto deletion, just like you are asking for. For Jellyfin there’s a plug-in: https://github.com/terrelsa13/MUMC

Plus for some odd reason the layout on my shieldTV is an absolute disaster for some reason

That’s because Jellyfin’s clients are still mostly terrible. Jellyfin is the more flexible media server, Plex has the far, far better clients.