Thanks for the port! There are many bug fixes in Mogan which should be ported back to TeXmacs.
For Tangdouer's PDF project, we'd better also upgrade the PDFWriter later. I don't know if tangdouer's code work fine with the old PDF Writer.
This is the most important bug fix for CJK fonts especially for Noto CJK fonts. Upgrade to the latest PDF Writer and then we can set the default CJK fonts to Noto CJK on GNU/Linux. And then, for Chinese TeXmacs users, they no longer need to download the fandol font and then make TeXmacs work with Chinese characters.
However, upgrading the PDF Writer will lead to build failure on old Linux distributions. Because the latest PDF Writer requires a newer freetype library.