As I don't have any M-class gear myself, I have to rely on the info given in the mailing list threads mentioned on [1]. Though it will never hurt to try again if you have the hardware, as the threads were already from late 2017 and 2015 respectively. Things might be different now, although I have my doubts.[1]: https://wiki.debian.org/Sparc64#Installing_the_Debian_SPARC64_Port
Never hurts to try. At most, a coffee pot may be needed.
Or does one need to do a cross compile from some other platform of a kernel?No I don't think so. I believe support for Fujitsu's SPARC64 processors and accompanying chipsets is just missing in the Linux kernel currently.
Well damn. I have both M3000 and M4000 gear as well as many many older sparc type units. I think I should grab an old old unit and try there first as those chips and motherboards have been around forever. Dennis