The problem
is that there are only 2 branches---"main", which was last updated in
February (and therefore too old to work with an updated ConTeXt)

    https://build.contextgarden.net/dl/luametatex/main/

and "work", which is updated daily-ish (and therefore often too new to
work with the stable ConTeXt versions)

    https://build.contextgarden.net/dl/luametatex/work/

However, since my build/upload script runs daily, it's pretty unlikely
that the contents of the "work" branch will be any newer than the
ConTeXt TEXMF files, except in cases where I'm releasing to TeX Live
more than a day after an upstream ConTeXt version was released (which is
what happened for this first initial release, but shouldn't happen often
in the future). I don't really like this solution, so hopefully
you/me/Hans can figure something out so that it isn't necessary for
future releases.