There was some recent commits to the INDI 3rd party github that appear to allow for both usb and wifi connections to the 2i, not sure if that has made it into StellarMate yet.
Here is what I have :
Raspberry Pi4 with StellarMate OS
SA 2i connected via USB-A to mini USB-B ( not into the ST4 jack )
ASI120mm mini connected via USB-A to USB-C
I then use the EQMOD driver with a baud rate of 115200 . Guide commands are sent via the EQMOD driver. I can guide, dither, do RA GoTos, manually move the mount in RA, and also Park and unpark the mount ( return to vertical position ). I did have some issues with plate solving because the mount returns a DEC of 0.0 always, and this confuses some aspects of EKOS.
You cannot use the SA specific profile that derives from the AltAz base profile, this does not work.
There, however, should now ( or soon ) be two new StarAdventurer specific profiles included with the EQMOD driver that are called USB and WIFI that preset the baud rate and set up the wifi connection, and those are probably preferred going forward.