So here is what I’m thinking so far.
For the GPS and radios:
“3 identical simpleRTK2B boards” (ref)
Digikey has simpleRTK2B kits with the GPS module and antenna in stock
Alternatively, this kit from Mouser contains two each of simpleRTK2B, GPS antennas, and some “LR Radio North America” modules with antennas. I’d have to add another simpleRTK2B with a “good” antenna for the base station.
Or perhaps a “Holybro H-RTK Mosaic-H GPS Module w/ Dual Antennas” (ref):
One “H-RTK Unicore UM982 (Dual Antenna Heading)” for ~$250
Another “H-RTK mosaic-H (Dual Antenna Heading)” for ~$780
What do you get for more than 3x the price?
If I stayed with HolyBro: SiK Telemetry Radio - Long Range ~$90 / pair. Wow! these are 1 watt / 50KM. That should get around the house! I assume you would need a license to run that.
I suppose the upgrade (in price) to SparkFun’s SiK Telemetry Radio V3 - 915MHz, 100mW might be a more reasonable choice for my 2 acres.
What about LoRa? Spark fun has what appears to be a nice set for ~$180: SparkFun LoRaSerial Kit - 915MHz (Enclosed). It claims 9 miles. Is 480 bytes per second enough trhoughput?
For that matter, it looks like I could opt for the Spark fun ecosystem for all the GPS and GPS related radios. (ref)
For RTK the base station:
I have wifi available over most of the property and power is generally available, so I would consider using a small windows PC administered over WiFi using remote desktop. I have this little windows machine (KAMRUI GK3 Plus Mini PC) being used as a dedicated license server for some legacy software and it has been rock solid.
I’m not opposed to an rPI or some other system. SparkFun’s RTK base station is tempting - should be less messing around with configuration . . . right? I wonder if that can be connected to a radio that will send correction data directly to the rover.
“survey grade antenna” (ref) was mentioned.
If I went with the HolyBro ecosystem, it appears that their “H-RTK NEO-F9P w/ Base Station Antenna” is the good antenna and module for the base station.
A lot of HolyBro stuff is out of stock or unavailable. Hmmm. Is this the now normal orange tariffs or some other supply chain issue going on with HolyBro?
For the flight controller:
“a Matek H743-Wing” (ref)
Get FPV has it for ~$90
I also see the “Cube Orange” mentioned ($650 on GetFPV). Seems like it is overkill . . . for instance I would not want ADSB 
OK, it looks like the CubePilot The Cube Orange+ Standard Set does not have ADSB for a slightly less eye watering $546.
Interestingly, this page says “Previously known as Pixhawk 2.1.”
There is an incredible price delta between the Matek H743 and Pixhawk / Cube modules. Is that because something is given up on the Matek H743, or because the Pixhawk / Cube modules are complete overkill for a 2-d Rover?
For the RC transmitter:
I saw “ExpressLRS” and “RadioMaster Pocket” mentioned. (ref). The RadioMaster Pocket ($72 on GetFPV) seems very reasonable. I wonder if it has enough channels for my other needs (start, choke, throttle, clutch). Searching “ExpressLRS transmitter” on Get FPV brings up $325 beauties, but would anything on that radio be an improvement to the RadioMaster Pocket for these rovers?
For the RC receiver:
Does the flight controller include the RC receiver? If so, is something like the Matek H743-Wing compatible with ExpressLRS? Or do I need to get a ExpressLRS receiver and connect it to the flight controller.
Good golly. So many questions, so few answers.
Please chime in with any comments, advice, or mockery of the noob. Thanks for any assistance you can offer.