I had not understood that you used the --commit option, sorry for the misunderstanding.
Foreign distros are not treated specially, but configuration for substitute authorization could be missing as described at the end of [1]. I do not believe they are missing though: Could you try “guix pull -q” to disable any other channels? guix pull -q --commit=08360a2cd0f1c447c9ad25bef8ed317abcdb0c91 on my x86_64 Guix System laptop, like your machine A (that downloads substitutes), builds /gnu/store/1mwhp5crimgvqd4jmlfsj3017yk8vxsv-guix-packages-base-modules.drv whose store path is different on your machine B (that does *not* get substitutes). Regards, Florian [1] https://guix.gnu.org/en/manual/devel/en/html_node/Getting-Started.html
