`matrix-media-repo` is the only role that seems incompatible with the
changes introduced by Traefik v3, due to its use of `PathPrefix` with
regular expressions in a few places.

Regular expressions should now be used with `PathRegexp`, not
`PathPrefix`. Furthermore, they should follow the Golang regexp syntax,
as described in the migration guide:
https://doc.traefik.io/traefik/migration/v2-to-v3-details/#dynamic-configuration-changes