Stable download URL for the latest version of Rtools44: https://github.com/r-hub/rtools44/releases/download/latest/rtools44.exe
The stable URL for the arm64 version of Rtools44 is: https://github.com/r-hub/rtools44/releases/download/latest/rtools44-aarch64.exe
For all versions see the releases: https://github.com/r-hub/rtools44/releases
See https://cran.r-project.org/bin/windows/Rtools/ for the official web site to download Rtools44.