One oddity that does not assist compatibility between the SX126x and SX127x devices is the way they handle the ‘LoRa Sync Word’
The Semtech SX126x data sheet says;
Set to 0x3444 for Public Network
Set to 0x1424 for Private Network
And the SX127x datasheet says;
LoRa Sync Word - Value 0x34 is reserved for LoRaWAN networks.
So 16bits of ‘Sync Word’ for SX126x and 8bits of ‘Sync Word’ for SX127x.
Apparently Public Network = LoRaWAN network.
And yes for a Private (non LoRaWAN) network you set the SX126x to 0x1424 and the SX127x to 0x12.