rather than debugonce install.packages,
do debugonce(download.file).
When I did this I found I can cause the downloading with code like
.External(utils:::C_download, "https://cran.rstudio.com/bin/windows/contrib/4.0/scales_1.1.1.zip",
file.path(getwd(),"gotscales.zip"), FALSE,
"wb", FALSE, NULL, TRUE)
Thing is though, if your server is locked down by your firms security policies, they may not see kindly to your even attempting to sidestep it ... I could imagine scenarious where this couldput you in danger.
I know this is an R forum and not career advice, but if I was in your shoes I would talk to a sysadmin for the server. before proceeding in this direction.