[R] repository for ubuntu/linux mint for R 4.0.0

[ProfJCNash]

In updating (an older computer with) Linux Mint 18.3 I tried to add
the repository

deb https://cloud.r-project.org/bin/linux/ubuntu xenial-cran40/

as per the "Download R for Linux" instructions. This gave an error
that there was no Release.key file.

After some investigation, I found that

deb https://cran.r-project.org/bin/linux/ubuntu xenial-cran40/

i.e., CRAN not CLOUD. With this change, I could install R 4.0.

Is this a known glitch?

JN