If you do not trust it there's a document Here which guides you through downgrading manually.
On linux This requires qt and curl to be installed, how it is installed depends on your distro, but it should work on windows out of the box.
To run this get a binary from Releases for windows or run the following on Linux.
git clone https://github.com/Fallout-London/FOLON-FO4Downgrader.git && cd FOLON-FO4Downgrader && chmod +x Run.sh && ./Run.sh
Read the build document
Cornelius Rosenaa for making this
Hollowrider of Brighter Applications for helping move backend to SteamCMD
Michel for testing on windows
Skedone for helping finish Linux support up
thomascrha for helping fix all the small bugs
SteamRE for DepotDownloader
Zerratar for reference FO4-Downgrader
feathericons for icons
yjg30737 for his PyQtLoadingscreen script
