> Some more context might be useful:
> 
> Device A (which successfully built qutebrowser over a couple days)
> ~ $ guix time-machine --commit=deeb7d1f53d7ddfa977b3eadd760312bbd0a2509 -- build qutebrowser --dry-run
> /gnu/store/i9ir7a26gv1ii98b4bzgvxp1sx0akind-qutebrowser-2.5.4
> 
> Device B (trying to avoid building qutebrowser)
> ~ $ guix time-machine --commit=deeb7d1f53d7ddfa977b3eadd760312bbd0a2509 -- build qutebrowser --dry-run
> The following derivations would be built:
>   /gnu/store/6n9aq7l5x26xfgrbvws7gvscbzvq5gqn-qutebrowser-2.5.4.drv
>   /gnu/store/05wj7wf7bdlkm1ar58kpakvp52drrz7p-qtwebengine-5.15.10.drv
>   /gnu/store/7nmv55qqw62jwzrd650vm434s3wpi7i3-python-pyqtwebengine-5.15.9.drv

Those hashes are not comparable: i9ir..nd (A) is the hash of the built
store item and 6n9aq..qn (B) is the hash of the derivation that builds
the store item.

> I have noticed in the past that sometimes a package gets built twice
> with two hashes, so I went back and checked if device A had built the
> 6n9..5gqn qutebrowser store item reported by B in addition to the
> i9i..ind one A was reporting.  There was no 6n9..5gqn qutebrowser build
> on device A.  I don't believe I have never run guix gc on either device.

But I do think it is weird if the derivation is not present on the
machine that build qutebrowser. Would you mind sending the output of
`guix time-machine ... -- build --derivations ...` from both machines?
If they return a different hash you could maybe also check the returned
`/gnu/store/...-qutebrowser-2.5.4.drv` files to see what is the
difference between them.

- Saku