I am attempting to do what you were trying in this post.
I want to make a Emlid LoRa compatible radio that outputs to RS232.
Here is what I have done.
You got a little farther than I have. I just found your post this AM.
I know when the M2 is connected to the Emlid LoRa radio it is using 38400. I have put a T in the line and have it feeding both the LoRa radio and a RFD900. I have received corrections on my RS2 via LoRa and simultaneously a Trimble Ag monitor (FMX/FM1000) via a 3DR radio I attached to it.
I have not figured out how Emlid configures the radio. I know GPIO_0 lets the M2 know it is connected to the radio (from the documentation I am assuming it is connected to pin 5 of the radio, operation status). The M2 did not config it till I connected GPIO_2 so per the documentation pin 6 & 7 are used to config.
My next step is to monitor the communication from the different ports (RX/TX/GPIO_0/1/2). Hopefully, I can decipher what is going on to use a Nano to send configuration data to the radio and use it as a 3rd party receiver.