Big note that I am a technician class with not much experience.

To get long distances, you can either rely on prolongation (you radio signal follows the curve of the earth), or line of site (your antenna can see the other antenna directly).

For propagation, HF generally gives you the best distance. You can use digital modes on the 20 meter band with a General class amateur radio license. You would need a portable transceiver and antenna likely mounted on your vehicle.

For line of sight, your antenna will need to be 20-30 feet above ground surface to see over the horizon. Hypothetically portable with a dipole on a pvc mast. You can use digital modes on the 2 meter and 70 cm bands with a Technician class license.

To send and receive data, you need to connect both radios to their own computer and agree on a language. Most commonly, you use two different frequencies to represent ones and zeroes. There are established protocols, but I think the one that would best lend itself to data bursts is proprietary D Star.

Digital isn't something I've used yet, so hopefully I haven't given any bad information.

Rattlegram or similar with something like an RT10 (license free ism band 900mhz dmr with encryption) or Moto DTR (license free frequency hopping spread spectrum, tricky AF to intercept)