It noticed that no Package.resolved file was written (else, I would have deleted it too besides the three folders mentioned; I now also deleted %TEMP%\org.swift.foundation.URLCache). I also noted that the package folder was write protected, but this is this strange Windows behaviour when every folder on your computer is "write protected" but you can still write to those folders, and in this case SPM could actually create the .build folder in the package and write to it, so probably "write protected" means nothing here... So SPM is still stuck displaying "Fetching..." and no Package.resolved file is written. Even tried to execute it as Administrator, failed too, and deactivated the Windows firewall.