Ken,
Resolved. You are correct on both counts, only COM3 was offered, and this is a corporate laptop.
Not following best practices for testing (I implement erp software for global company for a living, so know better), I changed three things at the same time:
- right-click reinstall driver for COM6 in Device Manager
- downloaded the
ftdichip.com driver and reinstalled (I had done this previously, but see now I had not done it correctly)
- upgraded to CHIRP 20210814
COM6 is now offered by CHIRP, and works as expected. Thank you for the pointers!
Cheers,