I'm unable to use third party Finder Sync Extensions on macOS 15, first beta. They do not appear in the Extensions section, that is now in System Settings - General - Login Items & Extensions.
Someone else start a separate thread about this. If I find an answer, I’ll post it over there.
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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"