It seems to be a known issue with GCP. Leaving “Google Groups” related to GCP is a fix to this issue. You can track this Public Issue for more information.
You might have been added into a project through a group, so it appears in the project list. However, you have not been granted permission to modify the IAM of that project, so you can’t remove the group from the permission list.
As a workaround, you can leave “Google Groups” related to GCP and reload the GCP console webpage so that all your unknown/inaccessible projects will disappear from the projects list. You can find what groups you’re a member of, using this Google Groups link.
NOTE : You can leave the groups in order to lose the access, but there could be a situation where your email is added to a single role/permission and you would not be able to remove yourself from the IAM list.
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