Gary Johnson was a uniquely good Libertarian candidate (based on his results). That's partially because he ran twice in a row and didn't really take a break between campaigns. Se he ran continuously for 5 of 6 years, building momentum and name recognition. He was also a more plausible Presidential candidate than previous Libertarian candidates: a two term former Governor, his running mate for VP was also a former Governor.
I don't think the Libertarians are likely to have a candidate nearly as good as him again.
After the COVID-19 fiasco and the riots this year Ill bet these fringe candidates get hardly any votes. I just dont think voters are going to throw away a vote when they have very serious issues on their minds.
Most polls use likely as those who
a) say they will vote, and
b) say that they voted last time.