Would have to be voted on by state and signed by Governor. Unless Congress changes voting laws nationally, which currently are with each state.
I've never been a fan of 100% VBM. I agree that it makes fraud & abuse WAY too easy to pull off. But that website reads as hyperbolic parody.
I'm not sure how it makes fraud easier to pull off. You have to sign the envelope. If the signature doesn't match it doesn't count (and the voter would be contacted for verification). If the envelope had been tampered with it would show that it had been tampered with and it wouldn't count (and the voter would be contacted for verification). It's super difficult to commit fraud with mail-in ballots on a scale large enough to make any difference at all.
As I have brought up in this forum previously, but I know someone who could not be bothered to take the time to vote a few years back. So his wife voted for him and signed it in his name (making a reasonable attempt to make it look like his signature). It was flagged shockingly fast and the guy lost his voting privileges for two years. The system DOES work in Oregon, and whoever says different is clueless. This is just another transparent attempt by the current fascist in office to take us even further into authoritarianism.