Here in NJ, they sent out mail-in ballots to all registered voters for the 2020 election during the pandemic so people could choose whether to vote in-person and risk illness or from the comfort and safety of their homes.

It was so popular, that the state changed the voting rules to allow voters to opt to vote by mail all the time. I don't know how many did. I haven't seen any figures on it but I think it's an elegant solution to the whole mail-in/in-person voting debate.