Which is the best kernel git repo for the latest/greatest support for the Unmatched board?
I would suggest freedom-u-sdk aka meta-sifive, though this is maintained as a set of patch files applied via quilt to an upstream kernel, currently 5.11.14
There is also one generic RISC-V patch one dir level up. The next version of freecdom-u-sdk to be released shortly uses 5.12 and has 23 patches instead of 28.
In general, I would recommend carlosedp’s page as the best instructions on how to build from scratch.
With the patches from the master branch of meta-sifive applied to linux-stable 5.12.4 I was able to build a self hosted working kernel that boots Debian. thx.