>> It's a quad core POWER9 feat. SMT4 (4 threads per core, so all in all 16 threads)

> [...] so they could run on all 16 cores

As said, it's just 4 cores, but 16 hardware threads.

> we might be able to continue to use some of the native MorphOS PPC software
> (maybe not, since all existing MorphOS native software is running on an API that
> is Amiga compatible?).

I guess some adaptations in the source code to accommodate to new/altered API functions would have to be made.