The Solution Architect should recommend a Partner Community license for this requirement. This license is designed for external partners and allows them to access and interact with Salesforce data and features, including submitting and viewing cases and tracking opportunities. Additionally, the Partner Community license includes the ability to create and view dashboards within the community.

https://help.salesforce.com/s/articleView?id=users_license_types_communities.htm&language=en_US&type=5

For partners to log and view cases as well as track opportunities, and view dashboards within the community, the Partner Community license is the appropriate choice. This license is designed for partner relationships and provides the necessary access to Salesforce objects and functionality needed for these tasks. Salesforce's licensing guide outlines the features available with the Partner Community license, supporting this recommendation.