Could you give a steel-manned version of what the folks "on the other side" are saying / arguing? What are some reasons / arguments or potential evidence you've heard from people who believe the election was rigged? Which, if any, of these arguments do you entertain as a possibility and why?

Or on the other hand, is there any strong evidence or reasoning pattern that suggests that the 2020 USA election could not have been rigged? USA 2020 elections did not use transparent block-chain voting afaik but do you think that tamper-evidency properties of a different kind nevertheless existed in the 2020 USA election to the point that we can be quite sure that everything happened "on the up and up"? If so what are some of the most convincing or trustworthy mechanisms that may achieve the property of tamper-evidency?

Do you have a clear opinion on the matter, and if so: What are some reasons, arguments or evidence that causes you to conclude one way or the other?