Hi,
I think the uv5r driver is likely one of the most widely-used with chirp. So, I just spent some time converting it to work on python3 (which was pretty easy on the face of it). I've lightly tested it with one UV-5R I have, but it is a highly-nuanced driver, with clone support for many variants and versions.
Jim, could you check out the py3 branch and give it a good test with a linux machine? On a debian-based machine, that would require python3, python3-gi, python3-serial and I think python3-cairo to be installed if you don't already have them. Then just run "python3 chirpw" and maybe make sure in the Help->About box that it's running under 3.x.
Also making sure that it runs properly in python2 is important (i.e. run the same chirpw with python instead of python3 and make sure it's cool there too).
Thanks!
--Dan