That was fantastic advice, thank you so much Quinn! I was able to create a minimal test project that reproduces the issue. You were right, the trampoline C file is the problem. And regarding your question: yes, it's only a single process that is launched by this trampoline C file. I opened a corresponding bug ticket: FB21015611

Thank you Quinn! You'd need to be logged in into GitHub to see the download button. I sent you the DMG via email in case you don't have a GitHub account.

Thank you so much Quinn for looking into this! I now changed the CFBundleExecutable to just Plover. The resulting DMG file can be downloaded from the Artifacts section here if you have a GitHub account. Sadly, the behavior didn't change and the menu bar icon is still missing.