It sounds like you'd be interested to get into ham radio. There are plenty of digital modes, and you can communicate all the way around the Earth in the right atmospheric conditions using a big enough antenna, or even bounce signals off the Moon.

There are videos of HAM guys scanning randomly through the spectrum to find people. I remember one video, 80% of it was static, and then a blip.. the guy (somewhere in the US) started to poke around that freq. another blip.. then a voice. It was a Russia dude answering, it was surreal.

APRS is something like that, popular with hams.

for just 'text' maybe something like LoRaWAN[1]

[1] https://en.wikipedia.org/wiki/LPWAN#LoRa