Comment by wjbolles

Yeah, there are admin APIs that can clear old images, local and remote ones. For your specific scenario you probably want this one:

https://matrix-org.github.io/synapse/v1.85/admin_api/media_a...

My server is not federated but fairly active, and we treat it as ephemeral. We've configured it so anything older than a week or two gets reclaimed automatically, text and media.