Non-partisans did side with Clinton in 16 and Biden in 20 but I can't find the margins offhand. Automatic registration has also helped make this figure larger. But it's a huge and growing pool of voters who we don't know with absolute certainly which whey they'll lean in a given cycle though they have AFAIK tended to be mostly younger voters.
54-41 for Biden. (46-42 Trump in 2016)
National Results 2020 President exit polls.
See National Results 2020 President exit polls.
www.cnn.com
The numbers on this page are estimates from exit polls conducted by Edison Research for the National Election Pool.