In the first link we see examples of ballots that have various markings, but only the word of Fox News that these are contested or "fraudulent" ballots.
"Substantial evidence" would include an assessment or report issued by a legal entity. Its a good thing the issue is in court -perhaps Coleman can get justice (assuming that it is deserved).
But neither link seems to be showing evidence of fraud but, rather, inconsistency in counting or hypersensitivity to rules such as omitting ballots with extraneous marks on envelopes.
Fraud would include a deliberate and intentional effort to sway an outcome. For that, there simply isn't "substantial evidence." At the end of it all, the court may rule it exists, but this is up to the legal system not pundits on Faux News or by-standers. The best they can do (and should do) is ask questions.