LaTeX Error: File `underscore.sty' not found

In order to allow underscores in a R Markdown script (whose output is pdf_document, with latex_engine: xelatex), I’ve added usepackage{underscore} and usepackage[english]{babel} (https://tex.stackexchange.com/a/321542, https://tex.stackexchange.com/a/561632).

It works for me, but not for my workmate’s environment.

! LaTeX Error: File 'underscore.sty' not found.

I guess the problem is that our versions of pdflatex and R are different (pdfTeX 3.14159265-2.6-1.40.18 VS pdfTeX 3.14159265-2.6-1.40.21 and R version 4.0.3 VS R version 4.0.2), but why does this error appear if we both have the underscore.sty file in the following path (according to locate underscore.sty): /usr/share/texlive/texmf-dist/tex/latex/underscore/underscore.sty ?

I don’t know if this is relevant, but he doesn’t get any output when he runs kpsewhich underscore.sty in the sell, whereas my output is the path mentioned above.

What is wrong with his setup? What do you recommend us to do? Thanks for the help in advance and sorry if this question or similar has already been resolved.