I am running Linux Mint connected directly a FT-991 radio. Up through version 2.2.20 rc3 work flawless. If I install the release version 2.2.0, it flat does not work. It will not communicate with the FT-992. Neither audio nor CAT control work, yet the pre-release version did work. Since the pre-release  version expires in a few days, I have had to revert to version 4.1.2

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C. Warren Andreasen - K7CWA
https://k7cwa.me