You request an absentee ballot with a signature which is then checked. You then receive your absentee ballot, fill it out with a signature, which is then checked. If things do not match you are given time to cure your ballot, whatever problem that may have occurred up to 3 days after the election. Uncured and unmatched ballots are not counted. If everything matches the ballot is removed and counted, separating it from the envelope signature.
I believe one insane remedy that Trump and other dipshits were proposing in some of their lawsuits, not just GA but PA and MI as well, was to check a random number of signatures on envelopes, say like 1,000 and determine if any of them under more scrutiny can be discarded. So say 5% or something claim don't match, then apply that 5% universally across the county or state, since more Biden voters used mail, he loses more votes than Trump and look at that Trump wins.