Yes, do try pushing the cable into your radio with more force, there is an issue of some cables not fitting the radio very well.
I forgot about this, otherwise proceed to my message about seeing if you're in the right group in your Ubuntu installation.
This is a normal usual step, often people do not read the various pages explaining how to install CHIRP.
CHIRP has such a page: https://chirp.danplanet.com/projects/chirp/wiki/Running_Under_Linux
It also says under Ubuntu the serial ports are in group "dialout" and tells you how to get your user into that group. Don't change "$USERNAME" that's just a universal shortcut for the user's username. In terminal do this: sudo addgroup "$USERNAME" dialout
*serial port permissions* Note that you may need to adjust permissions on the /dev/tty(something) device, or add your users who want to use Chirp to the "dialout" group in order to let non-privileged users access the serial device.
This issue is often indicated by an "access denied" error when accessing serial port.
On most Linux distros this is accomplished with:
sudo addgroup "$USERNAME" dialout
You will then need to log out and back in for it to take effect.
Regards,
David