Your videos are great and this is a really interesting experiment!

For a small budget campaign, since the videos are in english, I would set this language as filter to avoid wasting impressions in low conversion segments.

The landing page is a critical point, plebstr.com is good but it is just one app, and not open source (right?); we would need a captivating but simple landing page that could offer both a direct conversion goal (download an app, use a web client) and more generic informations for different kind of users (developers, content creators, business, etc). I cannot think of any resource that can fully meet these requirements; a good prototype might be https://getnostr.xyz.

Ideally the landing page should include the video itself and propose an easy way to share it outside the fb/instagram garden.