In other Markdown templates I’ve worked with, URLs were automatically hotlinked. Is that an option for Jekyll or am I just confused? (Both could be true of course. 
By auto linking in Markdown do you mean?
<https://domain.com/some-url.html>
Which converts to <a href=“https://domain.com/some-url.html”>https://domain.com/some-url.html</a>
What I meant is that without ANY markup at all, it would detect a link and auto hot link it. I believe Hugo did that. Maybe it isn’t as standard as I thought. I’ll try the syntax you suggested - that would save some time versus [url](url).
Would be up to whatever Markdown processor you use to do that since that’s what Jekyll relies on to generate the final HTML files.
Don’t think Kramdown does it without < > but maybe others do.
@mmistakes Is correct, kramdown does not support automatically detecting URLs and converting them into links.