The consent funnel seen as used on edgeryders.eu only applies to content that users post on edgeryders.eu themselves, or that ends up there automatically by being posted via our survey form software.
That survey software seems to be the best bet for your case, as it directly leads to a user account, post and consent on the edgeryders.eu platform but still provides a custom website, domain and styling so that it can be promoted by a third-party organization. That does not, however, allow for direct technical integration with their pre-existing signup process. (And my guess is that they also would not want that. Because who wants to do development effort to integrate with a third-party platform for a single event.)
For all other content you’d want to gater consent via other methods anyway. The methods in use are documented in our Consent Process Manual, and when there is a need other similar methods can be introduced.
I’d not be concerned too much about the GDPR aspect. Data sharing is legal when there is a legitimate interest and it’s documented in the privacy policy etc… The issue is more that we want to end up with properly documented consent for all content that is eventually used for research.