"What CPU instruction set architectures (ISAs) does Trisquel support today?
If I go to the download page today, I can only download images for Intel/AMD
32 bit or 64 bit CPU's. Are those the only two supported CPU ISAs?"
Sounds like you found your answer. :)
Trisquel 9 is supposed to have support for ppc64el and ARM. I'm not sure
which ARM since there are so many variants.
"Debian, the distribution Ubuntu is based on, does support RISC-V."
Not officially. It's in "ports", which is unofficial. Debian has some
requirements which RISC-V fails.
https://ftp-master.debian.org/archive-criteria.html
I imagine it won't "graduate" for a long time still; at least a couple of
years. Maybe more. It's hard to say. Even ppc64 still hasn't despite having
hardware available (POWER9.) The only difference between ppc64 and ppc64el is
endianness. ppc64 is big endian and ppc64el is little endian. POWER9 can
operate in both modes.
