having read about packages in "Mastering Shiny" (https://mastering-shiny.org/scaling-packaging.html) and the documentation of shinytest (https://rstudio.github.io/shinytest/articles/package.html), I turned my multi-file app into an R package. In an R package one removes all "source" and "library" function calls because your multi-file code is found without sourcing and because you import functions from foreign packages in NAMESPACE rather than using "library". However, after talking to shinyapps support (request #58728) I was told that one needs to use "source" and "library" when deploying to shinyapps. I was also told to submit a feature request here.
Thus, my feature request is to be able to deploy shiny apps that are packaged as R packages.