Considering some discussions in the parent thread, I think maybe it wouldn't hurt to ensure a minimal preamble when the output is compiled with LuaLaTeX or XelaTeX, so that some very basic fontspec configuration is loaded to be able to read PDFs in non-Latin scripts.
But before proposing the patch directly, I'd like to discuss its structure. I think (IMHO) that a certain balance should be ensured between a) users who don't want to mess with fontspec and want something more out-of-the-box and b) users who prefer to be in control when compiling with LuaTeX and XeTeX. I think maybe it would be nice to let LaTeX do the work, via a conditional from the iftex package (idea taken from pandoc). The structure of the patch could be this: 1. There could be a defcustom, something like 'org-latex-use-fontspec' (I would vote for nil by default). 2. There would be three variables for the default fonts: roman, sans and mono. By default, the FreeSerif, FreeSans and FreeMono fonts could be set as default value, since they are very ubiquitous and have a very good coverage for non-Latin scripts. 3. A variable (something like 'org-latex-fontspec-default-configuration') would return something like this: (format \\usepackage{iftex} \\ifpdftex \\relax \\else \\usepackage{fontspec} \\usepackage{unicode-math} \\defaultfontfeatures{Scale=MatchLowercase} \\defaultfontfeatures[\\rmfamily]{Ligatures=TeX} \\setmainfont{%s} \\setsansfont{%s} \\setmonofont{%s} \\fi org-latex-fontspec-mainfont org-latex-fontspec-sansfont org-latex-fontspec-monofont) (and this string would be added at some point to org-latex-make-preamble) 4. Conclusion: I think the good thing about letting LaTeX do the conditional work with iftex is that it saves us less invasive code on our end. I also think that other more complex approaches, such as searching for the fonts present in the system and adding them according to the document scripts, would lead us to a completely slippery slope. Of course, a list of recommended free-licensed fonts could be included in the documentation. WDYT? Best regards, Juan Manuel