Almost any third party candidate will benefit Trump. As we see in poll after poll, by historic margins Trump supporters are voting FOR Trump, whereas Biden supporters are NOT voting FOR Biden - but AGAINST Trump.
I'm positive Trump would have won the popular vote back in 2016 if not for Gary Johnson, who ran on the Libertarian party.
My brother voted for Johnson back then. I think he'll be voting for Trump this year. Libertarian party seemed to be comprised of "dudes," and I can't imagine any of them voting Democrat.