I concur! Menu bar apps behave differently on macOS, Linux, and Windows. Trying to use a cross platform solution is just going to result in 3 crappy apps.
Building a simple menu bar app for the Mac in Swift can be accomplished in a weekend (if you have no prior experience). If you need help with that, email me and I can give you a few tips.
If your app does more complicated things, you might want to write some shared framework in C++ that does the heavy lifting, but even then the UI should be written using native libraries.