Support for pc98 has been completely removed:
It's still listed at:
among others ...
Add ia64 to that.
Note that new platforms like aarch64 should probably be added, too.
One rather visible place old platforms are still mentioned is in https://www.freebsd.org/doc/handbook/bsdinstall-hardware.html .
It's only removed in head. pc98 is still present in stable/11 which is still a supported branch, so remove it from the website and docs is quite premature. ia64 was removed in 11 so is a bit older, but most of the existing references on the website document this clearly.
The bsdinstall-hardware page is definitely stale. ia64 probably can be removed from that, but also arm, and aarch64 need to be added, maybe powerpc64, etc.
We can remove sparc64 too when stable/12 is end of life.
technically pc98 and armv5 should be added to the list of old platforms, but I am not sure it is worth the effort