You can run multiple versions of R with RStudio Server Pro, and you can select which to run in a dropdown.
The open source edition does not have that ability to change R executables on the fly. That's find.
I just want to be able to pick somehow which of my installed R versions RStudio Server is using. This documentation says
If you are running RStudio within a web browser then the version of R is determined by whatever version of R is running alongside RStudio Server.
What does "alongside" mean? Is there a config file somewhere where I can give the path to the executable I want?