Possibly a reference to the fake electors plot [0], although there was also the phone call to the Georgia secretary of state asking him to find 11,780 more votes [1], the pressure he applied to his VP to reject the election results [2], the subsequent Jan 6 riot that disrupted the certification...
At least some of these were covered by BBC [3, 4].
He also tried to get the DoJ to label the election as suspicious. Don’t have an immediate reference for that but it was surfaced by the Jan 6 committee.
At least some of these were covered by BBC [3, 4].
[0] https://en.wikipedia.org/wiki/Trump_fake_electors_plot
[1] https://en.wikipedia.org/wiki/Trump%E2%80%93Raffensperger_ph...
[2] https://en.wikipedia.org/wiki/Mike_Pence#Vote_counting_and_s...
[3] https://www.bbc.com/news/election-us-2020-55524838
[4] https://www.bbc.com/news/election-us-2020-55559172