I tried using RLink today on a new silicon Mac. The silicon (ARM) version of R is installed and works. When I run InstallR I get the following cryptic error message. "InstallR::bndlunsupp: RLink does not support bundled R runtime for the current platform. Please use externally installed R distribution"
Ok. How?? I've looked at the RLink documentation and it discusses a "TargetPlatform" option, but it is not a model of clarity and does not provide examples.
I wasn't aware of your question until today, otherwise would've posted this answer earlier. It does generally make sense to cross-post questions to Mathematica at Stack Exchange, since some people (myself included) monitor that venue more frequently than the Community.
I have lost the battle with online editor here to make a minimally nicely formatted reply, so I will instead attach a text file with instructions, to this post. The notes in that file will be the basis for part of the RLink documentation for V13, for using external R versions with RLink. The workaround given in the notes, used for launching InstallR on Mac ARM, will also be removed / made internal, so that the user will not have to do it manually. However, some portion of the instructions (in the "one time configuration steps" section) will generally be always necessary for bleeding edge versions of R, since RLink's R library support usually lags somewhat behind.
If something in those instructions does not work for you, please let me know.