R check warning: Files in the 'vignettes' directory but no files in 'inst/doc'
I had a similar issue with an Rmd vignette. I fixed it by changing the YAML header of the vignette to something like this:
---author: "Name Surname"date: "`r Sys.Date()`"output: rmarkdown::html_vignettevignette: > %\VignetteEngine{knitr::knitr} %\VignetteIndexEntry{Title of your vignette} %\usepackage[UTF-8]{inputenc}---