At the risk of going off topic, is this an .Renviron setting? If I go the suggested RSPM route of going into Preferences:Packages outside an active project and configure 'https://packagemanager.rstudio.com/all/latest' as my URL, then create a new project and activate renv, install readr, put that into a dummy script, and snapshot, I still get CRAN as the repository in the renv.lock and CRAN in the individual packages in the lockfile.