How does your platform team gather feedback on what they build? Is it ad hoc or is there a formal process for hearing from developers?

By definition, 'platform' will serve multiple teams. So, it is good to take feedback - but I believe feedback is too late. Product manager of platform should talk to users of platform BEFORE defining roadmap of platform. And when are competing priorities from different teams, organisation interest should decide final priority. 

After features are delivered, formal feedback discussion is must to see platform is doing right job.  

Our COE (Center of Excellence) team bridges the developer community and platform development squads. They provide platform roadmap updates, hold office hours for feature deep dives, demos, and Q&As, and maintain communication through chat groups and surveys.

This setup allows us to engage developers closely, vet feature requests, and triage issues promptly, enabling development squads to focus on platform development. Roadmap and prioritization are informed by both architecture and COE-vetted developer input.