Hmmm, it doesn't say in https://lnav.org/features#automatic-log-format-detection but i see that at least json (and xml) is mentioned under the pretty-printing header.

You would know what is supported what with you being the author, just saying that the docs aren't super clear from a quick glance :).

And yes, I second the suggestion to focus on JSON. The main benefit of logfmt is that it's simpler for a human to parse directly but in general you probably shouldn't aim for that so..