This device, heltec v3, is basically as inexpensive as you can get and works perfectly well. The board itself is an ESP32 and is upgradeable with a better antenna. The ESP32 is not very energy efficient, so for low power & solar applications the RAK WisBlock devices are better. Lots of options here:

Devices | Supported Hardware Overview | Meshtastic

Detailed documentation on Meshtastic supported devices, including hardware specifications, performance comparisons, and guides.

Personally I think this outdoor solar node is really cool. Supposedly it will handles heavy rains well. I just need a high up location to mount it. $100 on Etsy #meshtastic