Flash ubuntu to sd and the ssd. Use dd or official imager etc.

Delete partition 2 from sd (fdisk, diskpart, gparted, Windows disk management)

Delete partition1 from ssd.

Plug both in and turn on.

Mine works fine, the largest file I have played was around 9gb streamed over gigabit and then wireless to the LG Plex app. Not sure what’s wrong your setups?