I am trying to install R 4.0.3 on a Raspberry Pi 4 running Ubuntu 20.10 64-bit. It is fully updated.
Before I did anything, I added the correct CRAN repository for this OS using
sudo add-apt-repository 'deb https://cloud.r-project.org/bin/linux/ubuntu groovy-cran40/'.
When I run
sudo apt install r-base, I get an error that r-base-core and r-recommended, both of which are specified to require version
>= 4.0.3-1.2010.0, are "not going to be installed".
Checking them individually, it seems that r-base-core is the problem. If I try to install r-recommended by itself, I get an error that it needs "r-base-core (>= 4.0.3-1.2010.0) but 4.0.2-1build1 is to be installed".
If I check https://cloud.r-project.org/bin/linux/ubuntu/groovy-cran40/, I notice that r-base-core 4.0.3 is only available in an AMD64 variant, per the amd64 in the filenames. I observe that the r-base package's files do not have amd64 in their filenames. To me, that suggests that, currently, you're only running R 4.0.3 on Ubuntu 20.10 if you are on an Intel/AMD 64-bit platform. https://cloud.r-project.org/bin/linux/ubuntu/groovy-cran40/Packages seems to back that up.
Are there practical alternatives, other than to wait for an r-base-core 4.0.3 package to appear that is compatible with more platforms?