Pennsylvanians should think twice before passing a constitutional amendment for universal vote by mail. The vote-by-mail system was a complete failure in 2020.
According to federal data, the commonwealth lost track of more ballots than the difference in votes between Trump and Biden.
Also in 2020, Pennsylvania set a record for the highest number of rejected mail ballots by election officials.
Mail balloting leads to disenfranchisement because errors are not able to be fixed in person like they are at the polls.
Same source as OP.