The story is part of an emerging pro-Kremlin disinformation narrative seeking to delegitimise the conduct and results of the 2020 US Presidential election.
So far no evidence of massive fraud has been presented except rumours. Several reliable sources debunked the massive fraud claims: the BBC, The Guardian, the New York Times, Forbes, Le Monde.
In addition, in its interim assessment on the conduct of the election, the OSCE finds that the contest was "competitive and well managed" (p. 1), noting that "evidence-deficient claims about election fraud" (ibid.) have been refuted by "election officials at all levels" (p. 3) and "national security agencies" (p. 11).
See similar cases that there was massive fraud in the 2020 US presidential elections, that two million dead people voted for Biden, and five facts that prove the US elections were rigged.
This disinformation message appeared in the same article as the claim that there is no evidence of Trump collusion with Russia.