In Visual Studio Code at least, you can force a Javadoc comment to respect line-breaks by wrapping it in triple-backticks, as seen below:
/** ```markdown
* This content is rendered in (partial) markdown.
*
* For example, *italic* and **bold** text works, but [links](https://www.google.com) do not.
* Bonus: it keeps single line-breaks, as seen between this line and the previous.
``` */