Re: LaTeX export: when is it more useful to use LuaTeX instead of pdfTeX?

[Max Nikulin]

I'm sorry, again, replying to the private copy of the message sent as 
Cc, I dropped mail list address at first.
Please, consider my response in the following context:

https://list.orgmode.org/orgmode/87a69j9c6s.fsf@localhost/
Ihor Radchenko, 2022-07-09:
> Or we may go even further and make org-latex-compiler default to luatex.
> This will benefit all the non-latin language users.
On 09/07/2022 21:58, Juan Manuel Macías wrote:
> Max Nikulin writes:
>
> > LuaTeX uses Latin Modern
> > and it is not nearly Unicode
> Maxim, please look at this screenshots carefully:
>
> https://i.imgur.com/uMfheCL.png
This set of characters is covered by latin-1.

> https://i.imgur.com/WwGybBA.png
Characters from Latin scripts, the set is wider than latin-1 but does 
not cover other languages. I do not dispute that font encoding is 
Unicode (if it can be stated so), usually support of Unicode is 
associated with smooth experience with wide range of languages.
> Frankly, I don't know what Latin Modern you're referring to, and what
> you mean by saying that "it is not nearly unicode".
/usr/share/texmf/fonts/opentype/public/lm/lmroman10-regular.otf I 
noticed in the LuaLaTeX log. Do you get non-latin characters with my 
example (without modifying \setmainfont) on your machine?
> \documentclass{article}
> % ================
> \usepackage{fontspec}
> \setmainfont{FreeSerif}
> % ================
> \begin{document}
> Abc — Αλφάβητο — Азбука…
> \end{document}
>
> \usepackage{fontspec}\setmainfont{FreeSerif} is the same as choosing the
> font in the libreoffice font menu.
I rarely use libreoffice, so settings should be close to defaults. I can 
just paste this text and I see whole snippet without additional actions. 
I have no idea why Liberation Serif is chosen, but the default font has 
much better coverage, so it is suitable for more users.
> But I think
> that this basic example that I have put is quite simple, and gives the
> user the freedom to choose his preferred font and not the one imposed by
> the system.
My point it that such freedom is not for free. If you know which font 
you would like to have in a book, you are ready to add some settings and 
LuaLaTeX has advantages in such case.
But for default settings getting blank instead of text in some routine 
notes is hardly acceptable. Unfortunately \setmainfont is not enough. 
Starting for "the simplest of basic" on the next step a user may notice 
that bold or typewriter text is missing.
So LuaLaTeX should be a conscious choice of users ready to add set of 
fonts for each language used in the document. I do not try to say that 
LuaLaTeX has no advantages. Application such as browsers or office has a 
feature suitable for routine documents: graceful degradation in respect 
to glyphs missed in the specified font. For publishers in some cases it 
may be a disaster (however I believe that ideally such issues should be 
discovered from logs even when not apparent from visual appearance of 
the document).
I am unsure if it was made by design or TeX engines with native support 
of Unicode fonts should made another step further, but currently Org is 
able to provide default preamble for PdfLaTeX, but not for LuaLaTeX and 
the latter is at least not trivial.