There's no need to downgrade R when you adjust the RTermPath setting in Zorro.ini or simply install/update R in a default directory minus the version number, 'C:\Program Files\R\' in my case. Then you only need to adjust the RTermPath path once. Make sure you backup Zorro.ini as it will be overwritten when you install a Zorro update.
I use R 4.2.1
I only use a CPU for processing, so I can't help you with your GPU issue.
I believe the R version does not matter, but a new R installation could solve issue with incompable Keras and Tensorflow versions. We found that when Tensorflow or Anaconda was already installed on a PC, Keras just uses the installed versions regardless whether they match or not. That was probably the reason for the issue.