Huh? Almost EVERY single state has mail in votes. How could that violate the Equal Protection clause? That is a bizarre argument.
I have read most of the filings and court opinion in these election lawsuits (although I have got a bit behind). I'm not reading an 86 page filing.
I would hazard a guess that it is related to the totality of the complaints Trump and his supporters have raised concerning elections in Pennsylvania: extended receipt date, signature matching, wide spread use of mail in voting, no decision on election day, delays in counting ballots, red mirage and blue shift, poll watchers, ballot counting watchers, etc. At 86 pages it probably rehashes all of these things in great detail.
The argument would be that people who voted in person at the polls are disenfranchised under the equal protection clause because they cast votes that they feel may be invalidated by the mismanagement of the mail ballots.
Of course, this argument fails for a number of reasons.
First, there is no evidence of mismanagement, only claims of mismanagement.
Second, people are not disenfranchised just because they feel that they are disenfranchised when that are not in fact disenfranchised (at least in this case).
Third, the only reason some people may feel disenfranchised due to distrust of the mail votes is because of the words and actions of Trump and his supporters. If Trump had not raised these meritless claims about mail ballots, they would not have felt this distrust.
Fourth, there is equal protection. Both Democrats and Republicans (and everybody) have the right to vote by either method.
Finally, if anyone is disenfranchised under the equal protection clause it is not the people who cast ballots at the polls but the people who cast the mail ballots or wanted to cast mail ballots. I wanted to vote my mail this year because it would be safer. I did not because there was controversy and lawsuits here that led me to suspect that a vote by mail may not be counted. I chose to vote in person because of my distrust. The distrust created by Trump that deprived me of the confidence that my legal vote by mail may not be counted.
They are really scaping the sludge on the bottom of the barrel here.