Update Contributing file

General +1 from me on this. In my evaluation of the CONTRIBUTING file, I didn't consider that setting up a working SSH key with Gitlab was a prerequisite. 😮

Might be even better to state the root cause and add a link to the doc page for setting up an SSH key?

You probably do not have a valid SSH key configured for accessing repositories on drupal.org. See <page> for setting one up or explore the following alternative options.

Until the README stops pointing to the CONTRIBUTING file, this seems safest. Ultimately there will probably have to be different instructions for people wanting to contribute/commit to the project and for those that are simply trying to casually use a pre-release to see what's coming.

Ultimately there will probably have to be different instructions for people wanting to contribute/commit to the project and for those that are simply trying to casually use a pre-release to see what's coming.

Yep, this!

For now, the pre-releases you can easily try are those at https://www.drupal.org/project/experience_builder/releases → — so currently only 0.1.0-alpha1. Subsequent 0.x.0-alphas will appear in the future, the first one at the end of February.