I saw yesterday that diff.blog's bot account on Github had starred the repository for this website. I clicked through to their Github page, which described diff.blog as
an aggregator of developer blogs… started in 2019 to improve the visibility of self hosted blogs.
I followed the directions in their README and signed in to diff.blog with my Github account. Once there, I added the URL of my blog to my account settings and diff.blog crawled my RSS feed. Once I saw how it was using the RSS item descriptions to generate summaries, I improved my build script to actually generate a description instead of just a list of tags. Now my blog is fully functional on diff.blog!
How did they find me? diffblogbot seems to crawl Github looking for blogs like mine. Looking at a random sampling of their stars, it seems that the crawled repositories are all Github Pages sites that either mention the keyword "blog" or have an RSS feed. Mine has both; I just recently added the RSS feed.
I went looking for other discussion about diff.blog.