FWIW the Firefox build instructions [1] look a lot saner to me than the Chromium build instructions [2].
[1] https://firefox-source-docs.mozilla.org/setup/linux_build.ht...
[2] https://chromium.googlesource.com/chromium/src/+/main/docs/l...
And one would hope they stay there, because all the newer stuff is far more user-hostile.