When I export my private key and add more user IDs to it, GPG adds extra feature flags that apparently aren't supported in Thunderbird. I've tried following the directions here, but GPG doesn't seem to do anything different with the --rfc4880 flag, and so importing the key back into Thunderbird still gets the "unsupported features" warning. Even when creating a key in Sequoia-PGP, it seems to add an extra notation? And that also seems to make Thunderbird say it's an extra unsupported feature. Am I doing something wrong?