On 18 Sep 2020, at 11:43, Thomas A. Schmitz wrote:

Then tell us a bit more about your system. What is the output of

which -a context

/Library/TeX/texbin/context

which is an alias of

/Library/TeX/texbin/context@ -> ../../texmf-dist/scripts/context/stubs/unix/context

and texbin is

/Library/TeX/texbin@ -> Distributions/Programs/texbin
/Library/TeX/Distributions/Programs/texbin@ -> ../.DefaultTeX/Contents/Programs/texbin
/Library/TeX/Distributions/.DefaultTeX/Contents@ -> ../TeXLive-2020.texdist/Contents

for example? Is

/var/folders/

the normal path where mactex would expect a format file? I use a Mac, but I have vanilla texlive installed; I never quite understood where mactex was any better, so I can’t test on my system.

The directory name luatex-cache suggests it's used for caching. I interpret the output like „something happens during the generation of the format file and therefore the file never gets generated“. I don't know much about the internals.

I don't really have any reason for using MacTeX over texlive; I was once told that this is the thing I want to use on a Mac when I was a student, and have used it ever since.
I could switch over and try texlive if nothing else helps, though I think it would be good to pin down the cause of this error and tell the MacTeX folks about it.

Regards,
Felix