Hi Ludo,

Thanks for testing!

It seems that we are experience something slightly different.  In my
case, it's not seconds but hours(!).

Also I cannot test on a warm cache because once the environment has
been built, then it's fast again.

It's only hanging seemingly forever if the environment is not built yet.
I suppose this has to do with substitutes indeed.

I'll with with --no-grafts and --no-substitutes.

-- 
Pierre Neidhardt
https://ambrevar.xyz/