After $ sudo apt-get install btnx I also got these messages at the end of the installation output.
Setting up btnx (0.4.11-3ubuntu2) ... Starting btnx : Button Extension - mouse button rerouter daemon btnx: uinput modprobed successfully. btnx: Could not read the config manager file: No such file or directory Segmentation fault (core dumped) btnx failed to start (error code 139) - try btnx-config
After $ sudo apt-get install btnx
I also got these messages at the end of the installation output.
Setting up btnx (0.4.11-3ubuntu2) ...
Starting btnx : Button Extension - mouse button rerouter daemon
btnx: uinput modprobed successfully.
btnx: Could not read the config manager file: No such file or directory
Segmentation fault (core dumped)
btnx failed to start (error code 139) - try btnx-config