It seems that when running this code

R_versions <- c(unique(stats::na.omit(stringr::str_extract(readLines("https://cran.rstudio.com/bin/windows/base/", warn = F), "[1-3]\.[0-9]+\.[0-9]+"))),
stats::na.omit(stringr::str_extract(readLines("https://cran.rstudio.com/bin/windows/base/old/", warn = F), "[1-3]\.[0-9]+\.[0-9]+")))

It only gets R versions up to 3.6.3

\Magnus