If installing the cauldron package leads you down a rabbit hole of dependencies, then your only choice is to recompile R-base for mga2.
You can do this either by compiling the tar ball, or my preferred method which is to rebuilt the source rpm (srpm)
There is a guide at
https://wiki.mageia.org/en/Packagers_RPM_tutorialanother guide which may be be more useful to you is here
https://wiki.mageia.org/en/Packaging_for_beginnersthere is a meta package called task-devel (I think) which will install most of what you need.
To add to the guide here are a few tips when rebuilding packages.
1. download the cauldron srpm to ~/rpm/SRPM. install it as user with. rpm -ivh rpmname.srpm
2. move to ~/rpm/SPECS. as root run the command urpmi rpmname.spec. This will install (hopefully) all the dependencies needed to compile
3. As user run rpmbuild -ba rpmname. spec
If all the build dependencies are installed it will compile and place a new rpm in ~/rpm/RPMS
Good luck