The Georgia Secretary of State has posted some instructions on how minor parties can comply with SB 189, the new law that says if a minor party is on the ballot for president in at least 20 states and territories, it can notify the Georgia Secretary of State and the presidential nominee of that party will automatically be on in Georgia.
Here is the one-page set of rules, which says the documentation from other states and territories (that have presidential electors) is due August 23. This is only a regulation, not a law, and the Secretary of State is free to revise it. In practice, the deadline is too early. Petitions for presidential candidates in five states are not due until early September. Therefore, the Georgia rules ought to have a deadline in early September as well.
UOCAVA, the federal law that tells states to mail postal ballots to overseas voters, does not require the ballots to be sent until 45 days before the general election. That means the ballots need not be sent out until late September.