I make no claims about the validity.
The rumor is today, Christmas Day 2020, a 3 minute audio from July 2020 is going to be released. It purports to be of Biden referring to black lives matters as "darkie malarkey" and joking about Kamalas' intelligence and more.
Since few of these rumors every materialize I doubt this one will either but it's something to hope for.
If true, it’s two months too late.