• OS: ArchLinux
• R: 4.1.2

Code should be placed in three backticks as shown below

* installing *source* package ‘interactiveDisplay’ ...
** using staged installation
** R
** data
** inst
** byte-compile and prepare package for lazy loading
Installing package into ‘/build/r-interactivedisplay/src/00LOCK-interactiveDisplay/00new’
(as ‘lib’ is unspecified)
Error in contrib.url(repos, type) : 
  trying to use CRAN without setting a mirror
Error: unable to load R code in package ‘interactiveDisplay’
Execution halted
ERROR: lazy loading failed for package ‘interactiveDisplay’