How do I make the MathML line breaking automatically in PDF output?

1. mathml.pdf‎ 223.4 kB

Currently not possible I'm afraid, unless you use a non-MathML approach like the ways of doing equations using plain CSS.

How to do a non-MathML approach in Prince XML?

Any updates in MathML line breaking?

Not yet, no. The non-MathML approach is to use CSS like this:

https://www.w3.org/TR/mathml-for-css/

However it may be simpler to use a preprocessor to convert MathML to SVG.