This is an STM32 topic not AVR/Pro Mini. So off-topic.
AI-Thinker RA-01 module is 433/470 Mhz not 866 MHz.
WHICH Dragino gateway?
Is it 8-channel LoRaWAN compliant?
Be aware that single channel packet forwarders are are not LoRaWAN compliant and are not supported on this forum.