I have seen this article [1] being thrown around among my conservative friends, and while I do not have the statistics background to understand the detailed analysis, it seems to suggest some strange behavior around the reporting of mail-in votes. Not exactly evidence, but something that may have warranted investigation at the time.

[1] https://votepatternanalysis.substack.com/p/voting-anomalies-...

edit: I'm looking for folks to give their take on this analysis since I nowhere qualified. A good summary is the final two sections of the article.