apt install libliquid-dev
https://github.com/pothosware/SoapySDR/wiki
apt install libsoapysdr-dev libsoapysdr0.6 soapysdr-module-all
The original MMDVMHost application does not work with virtual serial ports. So we have to patch it (only a single line).
In file Modem.cpp change the last parameter of line 183 from true to false.
old:
m_serial = new CSerialController(m_port, SERIAL_115200, true);
new:
m_serial = new CSerialController(m_port, SERIAL_115200, false);
And compile MMDVMHost.
Upon start, MMDVMSdr creates a virtual serial port /dev/pts/1 and a symbolic link to this /dev/MMDVMSdr.
Use this symbolic link /dev/MMDVMSdr in the MMDVM.ini
[Modem]
Port=/dev/MMDVMSdr