Thanks - OK, so I needed to install it from the app store, but that's in now and it helped with rlang. But...
Now (following instructions) I need to start Rcmdr. This is what I get...
library(Rcmdr)
Error: package or namespace load failed for 'Rcmdr':
.onAttach failed in attachNamespace() for 'Rcmdr', details:
call: structure(.External(.C_dotTclObjv, objv), class = "tclObj")
error: [tcl] invalid command name "image".