Guides
The failures worth writing down are the ones that raise nothing. A render that crashes gets fixed the same day; a render that succeeds and produces the wrong document reaches a customer. These are fixes for that second kind, written for whatever you render with.
Missing fonts in headless Chrome on Docker
Why a slim image prints boxes instead of text, and why installing the Noto packages does not finish the job.
Arabic not showing in PDF from headless Chrome
Two failures wear the same complaint, and fixing the loud one leaves you in the quiet one.
Chinese characters not showing in a PDF
The text layer says the Chinese is there. The file size and the font list say it is not.
Russian and Cyrillic not rendering in a PDF
The one script where the fonts are usually innocent, and the Dockerfile is the wrong layer to reach for.
Hebrew not rendering correctly in a PDF
The letters are all there and the line reads backwards. Usually that is correct, and the test you reach for cannot tell.
Right-to-left text and layout in a PDF
The second half of the problem: columns, margins and a page footer that inherits nothing.