Adding the keybase specific page to Jekyll just requires adding a some additional frontmatter to the content that keybase gives you, then adding the file to the root of your site:
keybase.txt file in the root of your site, then add the frontmatter and keybase verification text as follows:
--- layout: false permalink: .well-known/keybase.txt --- <Pasted content from keybase>
Save that and start your jekyll server with
jekyll s, and you should find that the file is available at http://localhost:4000/.well-known/keybase.txt in plain text.