I actually setup a Raspberry PI Zero W with the RFD900x connected to it on it’s UART. Load when running mavproxy is around 0.6 while the thing is also doing DNSMASQ and Hostapd.
So, as for cheap options go - it works.
I didn’t do a test flight or so. Waiting for a power supply. I like this setup and it could be a very small package in the end, so easy to mount on a pole.