lacheck binary package in Ubuntu Focal amd64

 LaCheck is a simple syntax checker for LaTex that is based on a
 single-pass lexical scanner. This makes clear that there are a lot of
 LaTeX problems this program cannot find, although it will find most
 simple mistakes. Complex macro packages may, however, make it completely
 unusable.
 .
 This program was bundled with AUCTeX once upon a time and is best known
 from there.

Source package