You can now create entity particle relationships for geolocation field types. Also, the dropdown menu for the metadata relationship field type shows which entities are supported.
- Custom Metadata Types Support Geolocation Field Types Relationships
Support for entity particle relationships was introduced in Summer ’20, with the exception of geolocation field types. With Winter ’21, you can now create geolocation field type relationships. - View Supported Relationship Entities When Creating Custom Metadata Types
When you a create metadata type, the metadata relationship field type menu now shows you which entities are supported. In previous releases, entities for relationships were only shown if they had a Salesforce Classic, Custom Fields setup page. This restriction was removed.