Fine as a temporary measure, but I would like to understand where the problem comes from. Maybe something for @lkstrp?

Same. It is the same issue as the previously failing ci and only happens on arm macos. And I think related to a new highspy build. Will revert this, once this is solved.

@Uzaaft
The issue is fixed now. See #1325. You might need to remove your env and clean the cache of conda/ mamba.

The issue seems to come from the fact that highspy in conda doesn't have osx-arm64 support, even if the pip variant has.
Previously, pypsa-eur pulled in pypsa from conda, and its dependency graph looked after highspy in conda, and would fail on osx-arm64.

But pypsa on pip was fine since pip has a working version.

At least that's my understanding

I think that's exactly it. If you install pypsa 30.2 with the build version mentioned in the PR it will work, since the recipe is changed.