I am one of these DDs and also official kernel maintainer of the SuperH port. I am not responding to such roll-call messages because there is no new SuperH hardware on the horizon at the moment except for the stalled J-Core project.
> And besides the developers, the SH4 port had infrastructure issues, such as taking 6 days to build GCC: https://lists.debian.org/debian-release/2011/04/msg00173.htm...
Well, the current RISC-V buildds also take days to build GCC. On the other hand, the 64-bit SPARC machines have been among the fastest in Debian, yet there is no official port.
> So the answer to "why wasn't SH4 an official port" is likely "there simply weren't enough developers and infrastructure for supporting it."
I would argue that the main reason is that Renesas simply abandoned the architecture and replaced it in their own applications with ARM.
The prospective 64-bit SuperH port was dropped as well.