[magixx]

It's unfortunate but unless you're willing to spend quite a bit of money (or are willing to forgo compactness) these are hard to find especially for 3.5" drives.

Radxa did have the Taco and Mediasonic does make compact 4/8 bay JBODs bur these are USB only.

There are also various NVME to SATA/SAS adapters but these mostly make use of port multipliers and speed won't be amazing. You'll probably also want some SATA backplanes to make wiring less nightmarish but these are annoying to source at a reasonable price.

My latest idea I had for something semi compact and performant was to try and use a USB4 SSD enclosure with adapters to connect a full size PCIE card. You'd then get a Thunderbolt DAS theoretically.

[theyinwhy]

Be aware that TB 3/4 is only PCIe3, 4 lanes (each 8Gbit) = 32 gbit