Quite surprisingly it's hard to find a workable solution around this.
I have an EC2 instance launched with Ubuntu 18.04 distribution.
I do sudo-get install r-base but the installed R version is R3.4
I've followed the steps here below where it asks to edit the source.list file https://cran.r-project.org/bin/linux/ubuntu/README.html#installation
However, AWS declines the update as the source link is not secured.
Have you made sure you succesfully added the public key to the system?
This has worked for me fine in EC2 Ubuntu 18.04 to update to R 3.6.1. I also followed instructions given in https://cran.r-project.org/bin/linux/ubuntu/README.html#installation.
First, add the public key in the documentation´s "Secure APT" section. Run this in terminal:
$ sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys E298A3A825C0D65DFD57CBB651716619E084DAB9
Next, add modify your file /etc/apt/source.list by entering this command:
$ sudo add-apt-repository 'deb https://cloud.r-project.org/bin/linux/ubuntu bionic-cran35/'
Once that is done, enter this command and double check if AWS has not declined the update
$ sudo apt update
Finally, run this to get updates installed
$ sudo apt install r-base r-base-dev
I found this resource to be very helpful: https://www.charlesbordet.com/en/shiny-aws-3/#how-to-install-shiny-server
I ended up using AMI from this website louisaslett.com/RStudio_AMI/
It has some pre-builts libraries and installations.