I've found following to be good,

1) https://stleary.github.io/JSON-java/org/json/XML.html  (using org.json Java library)

2) https://www.baeldung.com/jackson-convert-xml-json (using Jackson Java library)

I haven't tested these Java libraries, for XML mixed content to Json conversion (you may, feed XML mixed content data to these libraries, and see what Json documents they emit and see if that succeeds and suites you).

But otherwise, these libraries are good for, other kinds of XML information.

Also, these libraries are writting for Java applications. I'm not sure, if that could be a constraint for your work.

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Regards,

Mukul Gandhi