Ground-to-ground is limited by the curvature of the earth(unless you're bouncing things off the atmosphere like with HF radio). Generally even with a repeater on a mountain nearby the best you can expect is ~100mi.

There are many spots on the Earth with longer LoS views. Here is an interesting list along with photographs people have made of them: https://beyondhorizons.eu/lines-of-sight/

The longest one with a photograph is 443km (275mi).

Comments like this are why I still read hacker news.

IIRC the above link was the frontpage not that long ago. Very interesting

Indeed, this was pure line-of-sight, as the gateway was within the radio horizon of the balloon. Ground to ground would be more impressive, we have already seen ground distances with LoRaWAN of 320+ km due to atmospheric ducting. We'll look for more data and do a post about that later.