synapse-product/docs/privacy_policy_templates

If enabling the 'consent' resource in synapse, you will need some templates for the HTML to be served to the user. This directory contains very simple examples of the sort of thing that can be done.

You'll need to add this sort of thing to your homeserver.yaml:

form_secret: <unique but arbitrary secret>

user_consent:
  template_dir: docs/privacy_policy_templates
  version: 1.0

You should then be able to enable the consent resource under a listener entry. For example:

listeners:
  - port: 8008
    resources:
      - names: [client, consent]