When starting any app on macOS - the top menu bar shows menus related to that application. This menu changes depending on the app that has focus. When switching focus to a connected ThinLinc client - the menu does not switch. When initially starting the ThinLinc client, it does show the correct top menu bar, and switching back-and-forth between a different app and the ThinLinc client login window does work fine. The problem is only seen with a connected ThinLinc Client window. Tested 4.12.1 tlclient on macOS 11.2.
Problem manifests with macOS 10.14 and 10.15 as well.
This is bug 3746 as far as I can tell, just that things have gotten worse. Closing as a duplicate of that. *** This bug has been marked as a duplicate of bug 3746 ***