The maintainer of the key has changed and apt-get install throws an error when trying to install R for Debian - this is during the Docker container build for Slingshot.
Instead of the old key signature E084DAB9, the new key is 95C0FAF38DB3CCAD0C080A7BDC78B2DDEABC47B7 (maintained by Johannes Ranke as listed here https://cran.r-project.org/bin/linux/debian/ ).
The maintainer of the key has changed and apt-get install throws an error when trying to install R for Debian - this is during the Docker container build for Slingshot. Instead of the old key signature E084DAB9, the new key is 95C0FAF38DB3CCAD0C080A7BDC78B2DDEABC47B7 (maintained by Johannes Ranke as listed here https://cran.r-project.org/bin/linux/debian/ ).
I cannot verify this works at the moment as it seems port 11371 is blocked for the key verification under eduroam so I cannot authenticate the package either way. Details under daedalus's comment under the question here: https://stackoverflow.com/questions/10255082/installing-r-from-cran-ubuntu-repository-no-public-key-error
I will revisit the issue in a little bit here under different internet and see if it works.