damned Catalina

Dear All

among disasters of the new operating system Catalina, this one concerns R.

Trying to install ?regtools"  the answer by Crane R consolle is 

unable to access index for repository https://cran.stat.unipd.it/bin/macosx/el-capitan/contrib/3.6 <https://cran.stat.unipd.it/bin/macosx/el-capitan/contrib/3.6>

The same  for ?devtools?. This happens on my Mac with Catalina OS. The same installation on same Crane R but  on a laptop of colleauge of mine endowed with previous OS (el captain) succeeds without any problem.

Any remedy to suggest?

Thanks a lot

Bruno