Since a couple days ago, many attempts to run 'guix package' or 'guix
pack' lead to:

substitute: updating list of substitutes from
'https://mirror.hydra.gnu.org'... 100.0%
substitute: updating list of substitutes from
'https://mirror.hydra.gnu.org'... 100.0%
updating list of substitutes from 'https://mirror.hydra.gnu.org'...
100.0%g'...   0.0%

This fetching stops after a few lines and never finishes, even after
leaving it running for a day.

Command:  guix package -i r-minimal

I've attached a trace of the substitute processes.

-- 
  Joshua Sierles
  joshua@joshua.si