Hey Johan - we deprecated both the Ambassador program and custom CSS options from Hashnode blogs recently. They weren't widely used and were blocking us from shipping other features.
You can still use Hashnode in headless mode - build a theme from scratch using our GQL queries and self-host. But you'd miss out on free Hashnode hosting plus the SEO and AEO optimizations we do to rank your content. https://github.com/Hashnode/starter-kit