Richard KD2ZIW had issue with getting PTT to work under ubuntu and later found the solution at:
https://www.thuben.com/amateur/software/fixed-devices
Below is the contents of the related file “Digirig_rules” that should go into: /etc/udev/rules.d/
# Put this file in /etc/udev/rules.d
#
# Your Digirig serial number
# ENV{SERIAL_NUMBER}="1ee9d7cf8e7ded119fbeae814fc49859"
ENV{MAJOR}!="?*", GOTO="Digirig_rules_end"
SUBSYSTEMS=="usb-serial", GOTO="Digirig_usb_rules"
GOTO="Digirig_rules_end"
LABEL="Digirig_usb_rules"
# Digirig
ENV{ID_SERIAL_SHORT} == "Digirig_1ee9d7cf8e7ded119fbeae814fc49859_A", SYMLINK+="Digirig-PTT", MODE="660", GROUP="dialout"
ENV{ID_SERIAL_SHORT} == "Digirig_B", SYMLINK+="Digirig-AUX", MODE="660", GROUP="dialout"
LABEL="Digirig_rules_end"