If you want wireless communication between microcontrollers, you almost certainly want boards with integrated packet radio.
The RFM69 modules have a working range of 100m with a clear line-of-sight connection. The RFM95 LoRa modules work out to about 500m under normal conditions, and have been tested at 2km with focused antennas.
The data rate for both kinds of radio is about 19.2kbps (about 1.8 kilobytes per second).
Adafruit makes processor boards with on-board radios that work in the 433 MHz and 900 MHz bands.
In general, higher frequencies are more prone to scattering and lose more energy passing through objects, so 433MHz radios are a bit better at long-distance connections and connections where you don't have a good line of sight from one antenna to the next.
433MHz radios are more prone to interference from high-speed USB signals (operating at 480MHz) though, and high frequencies make it easier to modulate signals. That makes the 900MHz radios perform a bit better in areas where there are a lot of other signals.
Adafruit has Feather boards with ATmega32u4 and SAMD21 microcontrollers for both frequencies and both kinds of modulation.
