This is still very much work in progress, but it does partially work...

Download & upload work. Reading and setting frequency, duplex, offset and frequency should work. Reading settings works. Decoding the CTCSS values works, but not setting them. DCS doesn't work.

The vendor name contains Chinese letters as the H-777 only has the vendor written on the radio in Chinese. This works in Linux Mint but should be tested in other O/Ses.