Thanks for the tip. Only working in one mode at a time is totally sufficient for my base case - using the dongle to connect to remote wifi with a directional antenna.

Promiscuous mode is a nice-to-have, very much so, but I can live without it.

I could swear I have a MT761x dongle laying around somewhere actually - no external antenna, but, if I can find it, it might be worth it to see if I can get it working just to verify that the driver you mention actually works. If so, then I could buy a dongle with external antenna.