Thanks for raising this issue — we recently re-named the "shotgun" distribution to the "metagenome" distribution for clarity. However, it looks like we forgot to update the name in the installation instructions . We will fix this ASAP.
In the meantime, the distribution does exist and should be possible to install... in the installation instructions just replace "shotgun" with "metagenome" everywhere it occurs. So, e.g., this should work:
And yes, you are correct, the "metagenome" distro (the distro formerly known as "shotgun") is what is needed for whole metagenome sequence data analysis with QIIME 2.
Please let us know if you still run into any issues!