I would invest in a NAS box that sits in the network with a physical cable connection to the playback device. Then you can keep the current "does everything I need it to do" playback device; and in future change that device without storage features dictating the hardware options. The initial up-front expense is paid back over time in lower effort and cheaper future updates.
NAS setup would also depend if user wants to run network media server on libreelec or on nas.
NAS setup would also depend if user wants to run network media server on libreelec or on nas.
Nope, the NAS can be just a dumb storage device in the network. You can push the local media DB there too (MariaDB, etc.) if you have more than one client, but Kodi is not a true 'server' app that supports 'client' devices. If you want to run alternate non-Kodi server apps that's a different topic, but displacing Kodi wasn't in the original question.
OP did not tell, if they are using Jellyfin or Homerun. You can get dumb NAS box and then regret it as its CPU can't handle transcoding and case does not have option for second GPU.
Lots of questions to answer when selecting or building NAS.
OP did not tell, if they are using Jellyfin or Homerun
Jellyfin does not support transcoding on the Amlogic hardware used in the current box and the OP is asking about an alternative to that box with local storage. So "being able to transcode using Jellyfin on the NAS" is not really part of the requirement, is it?
Nope, the NAS can be just a dumb storage device in the network. You can push the local media DB there too (MariaDB, etc.) if you have more than one client, but Kodi is not a true 'server' app that supports 'client' devices. If you want to run alternate non-Kodi server apps that's a different topic, but displacing Kodi wasn't in the original question.
Honestly this. You would then just need a way to expose your HDD as a samba share on your network. Some home routers even have a USB port just for this use case (using an enclosure for a HDD/SSD). You mentioned a tall NUC and I've actually tried on my NUC8i5BEH and for my uses it was okay (but just okay). The NUC supports M.2 SATA/NVMe SSDs and SATA HDDs/SSDs so on a device like this you could install LibreELEC to the M.2 SSD, and leave the SATA slot for your 2.5" HDD.
Or you can just use an enclosure for your HDD to connect it with USB to whatever device running LibreELEC you choose to use.
The OP was about wanting to use internal storage. That’s normally a good indication people don’t want things hanging out of USB ports.
NUC’s are historically great; right up to the point LSPCON chips appeared and started causing HDMI problems. They remain great; as long as they work. However we see continued issues that go unresolved in drivers and firmware, and if we can’t guarantee something will be hassle free we can’t recommend them.
My normal go-to recommendation is an RPi5; never the highest spec, but with the best software support. That’s not really fitting the bill though, although these days there are some crazy ‘PC’ cases that you can run a pile of storage from.
I come back to “if it works, don’t fix it” so keep the current HTPC and just get a NAS to handle data. I’d always recommend using a proper NAS not DIY kits or a pile of USB drives, because I value my data, and I want to use a NAS not add more to the list of things I have to actively maintain.
If we're going strictly by OP's desire to only use internal storage then the aforementioned NUC is a good place to start, or a tiny form factor PC from Dell/HP/Lenovo should suffice as those usually have the motherboard connector that allows you to connect a SATA ribbon cable. I find these work best as most modern "mini pcs" have dropped SATA connectivity completely so anything Intel gen 7-11 gen is usually a safe bet for me.
Models I've had success with LibreELEC Generic installed on an 128GB M.2 SATA SSD, and my media on the internal 2.5" SATA SSD:
Lenovo P330 TFF, Lenovo P340 TFF, Dell OptiPlex 7040 TFF (they all have drive trays too)
