Microformats?

[LeaVerou]

https://microformats.org/

In the preliminary data for State of HTML Microformats actually came up above RDFa in structured data technologies used, though I suspect many people don't realize that OG is actually RDFa. Anyhow, might be useful to parse that as well.

The algorithm to parse is described here and seems relatively straightforward.

A website you could use to test against is https://tantek.com/ , one of the creators of Microformats.