I’m in a similar boat, my Optiplex has a small m.2 expansion slot, I believe intended for a WiFi chip.
I nought a dual SATA card for it, just need to find a nice enclosure that will power 2 drives and provide a direct SATA connection to some 3.5" disks.
If anyone knows of some let me know!
The past few weeks I’ve seriously missed the content over at DataHoarder.
Was nice to see mention of this community over here, hope to see more activity soon.