Ah, this is a promising avenue! I have struggled with PATH issues before, and probably messed mine up trying to debug a ruby/jekyll issue a few weeks ago. Here's my current PATH:
> Sys.getenv("PATH")
[1] "/Users/amcnamara2/miniconda3/bin:/Users/amcnamara2/.gem/ruby/X.X.0/bin:/opt/homebrew/bin:/opt/homebrew/sbin:/Users/amcnamara2/miniconda3/bin:/Users/amcnamara2/miniconda3/condabin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/opt/X11/bin:/Users/amcnamara2/Applications/quarto/bin:/Library/TeX/texbin:/usr/texbin:/Applications/RStudio.app/Contents/MacOS"
Well THAT doesn't look right!
Running export PATH="/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin" in the terminal doesn't seem to make a difference to this, which probably means I have done something stupid elsewhere. My .Renviron file had one little PATH-related thing, which I've deleted and saved and I restarted R. Sys.getenv() still gives that long path with miniconda in it a bunch of times.
BUT searching on RStudio Community brings up this thread which suggests there is perhaps a bug in the RStudio IDE related to PATHs and Mac M1? Sigh. More to explore.