I think what Qt does is a good compromise, but there are breaking changes. Complex FLOSS projects spent months or years upgrading from Qt4 to Qt5 and then to Qt

I think what Qt does is a good compromise, but there are breaking changes. Complex FLOSS projects spent months or years upgrading from Qt4 to Qt5 and then to Qt6. The exact timeframe is a matter of priorities and available developers, but someone had to put a not insignificant amount of work into porting. A far cry from decades-long ABI compatibility.