Running R 4.0.5 on a Linux command line (RedHat Centos 7) and unable to install any packages. Checked for internet connectivity and it passed the test. Switched between CRAN mirrors using chooseCRANmirror() and didn't help.
Warning: unable to access index for repository https://cloud.r-project.org/src/contrib:
cannot open URL 'https://cloud.r-project.org/src/contrib/PACKAGES'
package ‘rlang’ is not available for this version of R
A version of this package for your version of R might be available elsewhere,
see the ideas at