"For proof, they point to the fact that voters are allowed to hand over their ballots to another person who submits them on their behalf."

That's true anywhere. Every community in America has shut-ins and people who simply cannot get away to vote in person or even to mail in a ballot, so sealing your ballot and handing it off to an associate, a friend or relative to post it or drop it into a "genuine" drop-box is perfectly legal.

If that's the definition of fraud, then I'm the definition of howler monkey.

"Ballot harvesting":
Having Democrat Party members go door-to-door to pick up ballots from Republicans and Republican Party members go door-to-door to pick up ballots from Democrats is simply begging for trouble.

"These Republicans appear to have committed felony election fraud."

That's all it will ever be until they complete their trial. Everybody is innocent until conviction. Warnings are in place, so we'll just have to wait it out and see what comes of it all.