It could target Win32, GTK and Qt all at compile time (even Android and OS X but that never got developed all that far AFAIK), depending what runs on your target platform, while you get common components and RAD at design time. I haven't seen anything like it since and sadly the language and ecosystem are mostly dead, which is a shame, because the idea was brilliant and it actually worked (and is still used in some software, like CudaText and PeaZip I think).
Unironically, FreePascal/Lazarus had a decent shot at this with LCL: https://en.m.wikipedia.org/wiki/Lazarus_Component_Library
It could target Win32, GTK and Qt all at compile time (even Android and OS X but that never got developed all that far AFAIK), depending what runs on your target platform, while you get common components and RAD at design time. I haven't seen anything like it since and sadly the language and ecosystem are mostly dead, which is a shame, because the idea was brilliant and it actually worked (and is still used in some software, like CudaText and PeaZip I think).
Aside from that, something like MAUI could be worth a look: https://dotnet.microsoft.com/en-us/apps/maui