Are there current JBOD products in 1U short-depth (15" for wall mounted rack) form factor, e.g. 4 x 3.5" hotswap drive bays with a mini-SAS connection to the unit? This would be useful as a backup device, or low-power NAS when connected to a Linux thin-client with LSI HBA.
There were some 1U products which included RAID support, priced around $500, which is a bit much for 1U chassis + SATA/SAS backplane + Pico power supply. 1U chassis with ~11" depth (seems to be a telco standard?) start around $100.
StarTech 1U JBOD discontinued, https://www.startech.com/en-us/hdd/sat35401u
Silverstone RS431 JBOD unavailable, https://www.silverstonetek.com/product.php?pid=482&area=en
iStarUSA upcoming (shipping in June) 1U JBOD is $400, http://www.scsi4me.com/istarusa-m-140ss-jb-1u-3-5-4-bay-tray...
For ~$600, QNAP has an Arm-based 1U short-depth NAS with 2x10GbE and 2x2.5GbE networking, plus dual M.2 NVME slots. Maybe Armbian will run on that SoC, it's part of a supported family. https://www.qnap.com/en-us/product/ts-435xeu
$100 ODROID M1 SBC has an M.2 NVME slot with 4x PCIe lanes. In theory, this could be bridged to a PCI slot + LSI HBA, within a small case, as a DIY low-power NAS.