One of my laptops now serves as a dedicated Ubuntu machine, acting as a perfect test device for testing apps and self-hosted ...

A 2TB Evo Plus is enroute to replace the existing 500GB version of the same M.2 drive in my system, and I have two M.2 slots on the mobo, one currently occupied by the OS drive and the other empty.

USB devices are block devices like any other. Linux doesn't care if you install or boot from a SATA disk or a USB disk, it makes no differences in that regard. The only niggle is can be BIOS support, ...