If you are getting an error starting geckodriver when using rselenium, you may want to try deleting the LICENSE.chromedriver file which accidentally attempts to be executed by wdman::geckodriver. You can do this simply in the Linux terminal by using this command. The xargs -r command only executes the rm command when there is a file matched to delete.

find ~/.local/share/ -name LICENSE.chromedriver -print | xargs -r rm