I ghettoed it. Might work for you.
Since my main nas was using all 6 satas I wanted to expand.
Got a PCIe SAS card, 2 SAS to SATA external cables, each cable goes to 4 satas.
For the disks I got a backplane for 8 disks, a random tower, a cheap PSU and have the sas to SATA cables going from one tower to the other. The PSU is jumped, I still need to get a button for it.

I just dumped the backplane in the case, nothing is fixed. Need to work something out, eventually.


For music I ended up using navidrome, and, on Android symfonium, which is paid (single payment) but so good, better than anything I tried at least a year ago. On a computer you can use any open subsonic client since navidrome exposes that