Problem with port 30104 & Airspy Mini/Odroid XU4

Maybe it was “fixed” on Pi3 (maybe not), but I am suspecting it might be something to do with the IPv6 implementation on that specific platform (Armbian 5.59 Odroidxu4 Debian stretch_next4.14.66).
I don’t have IPv6 enabled in router (nor by my ISP).