Dear fellow tikz users,
deleting /usr/local/lib64/R , recompiling and reinstalling R-4.2.0 and all the nice packages I'm using all the time, including tikzDevice, solved the problem I have described above. I fail to grasp why reinstallation of tikzDevice alone has not led to this result, but I can accept my limited understanding of the details now that tikzDevice works like a charm with R-4.2.0.
Kind regards,
Ernst