Dear Maintainer,

Maybe you have known this, valgrind support riscv64 since 3.25.0, see
the release notes[0] for 3.25.0.

I have tested it on my local Unmatched board based on the codebase[1]
with a new upstream release expect the need to let lintian happy, there
is no any issue to build it on riscv64.

So could you add build support for riscv64 on next upstream release
update? Or please let me know if I can help in any way.

[0]: https://valgrind.org/docs/manual/dist.news.html
[1]: https://salsa.debian.org/debian/valgrind