I need a simple, but robust C++ library that works well with ESP32. ESP32 with its ecosystem is good enough for the variety of projects. It's a good starting point. If for some reason ESP32 isn't good ...

LoRa ESP32 KISS Bluetooth modem (for APRSDroid or aprs.fi iOS) + APRS-IS RX/TX iGate over WiFi + Digipeater + DV (with Codec2 Walkie-Talkie) ...