"Official sources" are the counters and whatever office in any gioven state oversees it, and the count as it was confirmed Biden's victory in the way that media only counted a state as "won" if the count by that point is so far ahead, that even if all the remaining votes were all exclusively for the other candidate he would still win.

Yes there may be a second and closer count, but just based on historic precedence, they usually don't change any more than the 0.0XX% of votes, so usually just a few hundred votes per million voters.

And Biden's victory is WAY beyond that in all the important states.

It's as official as it gets. Trump's lawsuits just try to make them look less so, but all of his lawsuits are being laughed out of court by the judges due to their inability to provide any evidence. And when asked the lawyers usually answer that they have none, and that their claims of e.g. "no observers" were lies (because if the judge asks you as a lawyer, you answer truthfully. Or your career is over because you WILL be disbarred.)

Whatever you consider the "official sources" to be, they certainly didn't call the election for Trump.