Xastir is most likely what you want. http://xastir.org/index.php/Major_Features#SUPPORTED_TNC.27s:_DARN_NEAR_EVERYTHING.21
YACC - Yet Another APRS Client is also a newer choice. I have not personally tried it.
You could use Aprx or Direwolf and configure the client as a Receive-only iGate. You can then assist in sending some directly received data to APRS-IS (the Internet side of APRS) and see the data appear on sites like www.aprs.fi
You will need a password to be able to log to aprsis but this is trivial once you have a callsign and google for aprs password ...
Actually, direwolf already supports higher data rates since 2017; it will use the G3RUH modem for a speed of 9600 or higher. As shipped it can be configured up to 40000 bps.
But it's a mistake to think that 9600bps isn't making use of a 48kHz sample rate. The author has done some testing which shows that 9600bps is about the highest rate that works reliably ...
After pairing to the TNC, use the "cu.***" port as the address in Xastir.
For me it was: "/dev/cu.MobilinkdTNC2-DevB". Set the baud to 9600 and click done.
My connection failed after about 15 minutes. I unpaired, repaired, and then the connection stayed up.
You need the applicable reverse-polarized TNC adapter. Sounds like you have a standard TNC Female on your antenna
and a RP-TNC Female on your device.
Can you confirm?
Based on your comments I'm concerned that you are not certain of your determination of the existing connectors. (It's easy to confuse standard TNCs with ...