- You don't want to give more priority to non-Linux users
- GTK feels terrible on those other platforms
- You don't believe those who care about licensing issues would use it
- You cannot build releases or installers for Mac
The first thing that comes to mind on reading your response is that the non-Linux users are a market you are not really interested in - and even if they were they are not a market you can effectively serve (installers, updates, issues).
You should consider formally abandoning official support for non-Linux, as in reality you don't currently have actual support for them anyway. Be honest, cut your losses, and choose your customers. Cross-platform is not a benefit if it is unsustainable.
- You don't want to give more priority to non-Linux users
- GTK feels terrible on those other platforms
- You don't believe those who care about licensing issues would use it
- You cannot build releases or installers for Mac
The first thing that comes to mind on reading your response is that the non-Linux users are a market you are not really interested in - and even if they were they are not a market you can effectively serve (installers, updates, issues).
You should consider formally abandoning official support for non-Linux, as in reality you don't currently have actual support for them anyway. Be honest, cut your losses, and choose your customers. Cross-platform is not a benefit if it is unsustainable.