Since the N9 and N900 both use the same ARM processor, not too surprised there. Don't forget that the N8x0's are no longer supported for Qt. Give it time, it will happen in that area as well for the lower spec'd N900.

But no MicroB updates is a problem - can't run Google+ well/at all. Modest is open source, but no major updates there. The WONTFIX issues aren't fixed on the N900.

I wouldn't call that support. It's just yet to be considered obsolete by the frameworks you mentioned. N810 can't go above Qt 4.5 (or 4.6, I forget) and yet it runs Qt.

I'd personally rethink using the term support.