Permissions seem OK. That folder was owned by wwadmin with group www-data. I tried changing the owner to www-data, but that didn't change anything.
I also tried installing texlive-full; my install passed all checks, but just in case... This also didn't help.
The other thing I tried was uncommenting the part of localOverrides.conf that sets /var/www/html/wwtmp for temporary files, but that didn't make any difference.
I always get the same error messages as in my original post.
I also tried installing texlive-full; my install passed all checks, but just in case... This also didn't help.
The other thing I tried was uncommenting the part of localOverrides.conf that sets /var/www/html/wwtmp for temporary files, but that didn't make any difference.
I always get the same error messages as in my original post.