Perhaps this is already supported, but I screwed up. On most sites you can select the language for which the syntax highlighting should be applied by giving the language name after the three forward ticks like this:
This broke syntax highlighting completely for me when I tried:
The language name definition used by the tech stack here is `tex` not `latex`.
Also for the tex site, that is the default language, so you don't have to specify it. To disable, use `none` as the language.