Weird LaTeX error: File l3backend-pdfmode.def not found
For the past few months, LaTeX had been completely broken on my computer. I’d been hoping it was something systemwide and that upgrading LaTeX would fix it. Nope. I’d tried mitigating using different engines. Turns out, xelatex produces different line breaks (!!) and lualatex was somehow incompatible with acmart 1.73 on my computer (metric data for lmroman10-regular not found). Computers are great.
Here’s the pdflatex error message:
! LaTeX Error: File `l3backend-pdfmode.