No, there is no compatibility list out there, i am sorry.
The reason is that we are not parsing the recipes literally but use a standard that many sites stick to. If a site provider changes their (invisible) metadata, the import might suddenly work out fail:
Often, the standard is not adhered to by 100% and minor flaws are compensated by the cookbook app. Typically they check if Google’s rich text engine understands their data. If yes, they are satisfied.
This also means that each URL not the domain could be compatible or not. It would be more fine grained. The data that is parsed is just some sort of invisible “comment” within the HTML source code.
Does this make sense to you and answer your question?
Considering how a simple script using BeautifulSoup can easily extract even flawed structured data from any URL whether they use JSON-LD, RDFa or microdata, is it possible to have an external process fetch and extract from a URL and then submit json-ld directly into the Nextcloud recipes?
I think, I read this request recently somewhere. If you cross post, please add references, so and answer can be found.
The API is documented in Swagger UI. you can use the /api/v1/recipes request using POST in order to store a JSON directly.
As a side remark: the problem is known and a solution in general as well. The thing is that the parsing of graphs is a complete rewrite of the parsing algorithm and I want to avoid this to be reworked again after short time due to bad design decisions.