This happened in Roanoke, which is left leaning. Republicans are going all out to cheat in this election.
Edit: Here is the law on tampering with ballots in Virginia. Class 5 felony
https://law.lis.virginia.gov/vacode/title24.2/chapter10/section24.2-1009/
For mail in balloting at least in my state you sign the return envelope NOT the ballot itself.
In Illinois they give you two, well 3 technically. The one everything comes in, the one you put the ballot in, and the one you put the ballot envelope in. So the signature is not on the outside or on the ballot itself.