Greater than 99%, I'd say.
In April 2020, a 20-year voter fraud study by the Massachusetts Institute of Technology found the level of fraud "exceedingly rare" since it occurs only in "0.00006 percent" of instances nationally, and, in one state, "0.000004 percent — about five times less likely than getting hit by lightning in the United States". Even if voter fraud in this election were somehow 10 times more prevalent than the previous 20 years, which is highly unlikely, that's still only 0.0006%, which of around 146m votes is fewer than 900 votes. Across the whole country.
Even when Trump set up a commission into voter fraud, put the Vice-President in charge, and gave it majority Republican members, it had to disband as soon as a federal judge ruled it should share its workings with the Democrat members as well as Republicans. There simply wasn't the evidence.
Just last month, Republican election lawyer Benjamin Ginsberg wrote: "I spent four decades in the Republican trenches, representing GOP presidential and congressional campaigns, working on Election Day operations, recounts, redistricting and other issues... The truth is that over all those years Republicans found only isolated incidents of fraud. Proof of systematic fraud has become the Loch Ness Monster of the Republican Party. People have spent a lot of time looking for it, but it doesn't exist."
People can share and spread whatever "proof" videos and clickbait they like. The reality is that every time the cold light of fact and truth is shone on them, they melt away.
Joe Biden will be the 46th President of the United States. Donald Trump lost. Get over it.