Reported by @buzacott: #160

"the test-coverage action is failing and it seems like there is some compiling error on one of the dependencies to setup the action. After a quick look it looks like it is a fortran/macOS issue, but perhaps the action should be run using linux as software compatibility will be more robust there."

* installing *source* package ‘quantreg’ ...
** package ‘quantreg’ successfully unpacked and MD5 sums checked
** using staged installation
** libs
gfortran -mmacosx-version-min=10.13 -fno-optimize-sibling-calls  -fPIC  -Wall -g -O2  -c akj.f -o akj.o
make: gfortran: No such file or directory
make: *** [akj.o] Error 1
ERROR: compilation failed for package ‘quantreg’

I agree that moving to linux or windows might be a good option here, but not sure if there's anything else macOS specific in the github action. Fixing the gfortran setup might still be worthwhile.