Hello Maxime,
> Discovery of substitute servers on the local network doesn't seem to > work properly, see output of > `sudo guix system reconfigure config.scm --save-provenance` > at end of e-mail. Disabling substitutes (e.g. `guix build hello --no- > substitutes`) seems to work-around the issue. Thanks for the complete bug report. This is fixed with c952a9312a94bb236495ec654bf184685cf9fe79. Note that you will need to run "guix pull" before reconfiguring. Mathieu