If you refuse to look for it, you will never find it.
There have not been any meaningful investigations that I know of into it. Just people stating that there was no fraud or election commissioners saying they did nothing wrong when irregularities are pointed out. ie. blocking poll watchers from observing counting, removing poll watchers completely, not performing signature verification, explaining late-night delivery of ballots, running stacks of ballots multiple times through the machines, etc.,
No deep forensic audits have been conducted, yet. New Hampshire has said they are going to do one after they did a hand recount in one county and found the machines gave 8% of the Republican vote to the Democrats. Arizona is still fighting a county commission about doing one.
Georgia did a re-count where they ran the same ballots through the same machines again. They never checked if the machine counts were accurate. They never addressed the questions on signature verification, ineligible voters, or the machines being connected to the internet.
So far no court case filed has gone to trial or had evidence presented, all the court cases were thrown out on some technicality, including the SCOTUS case. ie. lack of standing, moot point after the election, too early to bring the case, too late to try the case, or saying it would not change the results.
