Might be irrelevant given the latest on Biden dropping maybe, but this is still the official line:_

“no voting will begin before August 1.” They add that the vote is set to happen before the in-person Democratic National Convention that starts Aug. 19

They’ve now explained the nuance and reasoning, which does change things a fair bit

In June, Ohio passed a bill to move its deadline from Aug. 7 to Sept. 1. But because that law technically does not take effect until Sept. 1, the DNC said they are keeping their timeline of a pre-convention virtual roll call in place due to concern of litigation. Republican Secretary of State Frank LaRose suggested earlier this month that Sept. 1 deadline to certify a candidate would stand.