Yes. It looks like you are wrong.
1. I did a clean install of the latest Linux Mint
2. installed CHIRP-next following the instructions on the Running CHIRP on Linux page
3. logged out and back in to activate the serial port permissions
4. downloaded from a UV-5R that was handy
Your issue may be due to still having the Britty screen reader package installed. Britty, which I think Mint installs by default, seems to cause problems with ttyUSB0. During the install, I had unticked the box at the prompt asking if I was going to use the Britty screen reader. This seemed to be enough to keep it from causing issues for me (so I didn't have to add any steps to remove it).
Jim KC9HI
