Wrote a blog post about a browser extension I made that adds mastodon (or mastodon compatible server) search results to DuckDuckGo

https://tomcasavant.com/duckducksocial/

Experimental addon is available for Firefox here: https://addons.mozilla.org/en-US/firefox/addon/duckducksocial/

Thought about using OpenSearch? Then you've got a standard and well-known solution that doesn't require a browser addon or proprietary API. If I recall, Mastodon also requires ElasticSearch, which pushes it even further into proprietary solutions to problems that were solved by open standards long ago. We've been using it in the fediverse for around 15 years.

Here's a recent spec:

https://fediversity.site/help/develop/en/Federated_Search