By law, South Africans who live abroad can only vote in South Africa’s NATIONAL elections (not provincial or municipal elections).
To vote in Municipal Elections you must be registered where you live in South Africa, and then vote where you are registered.
Unless you are already registered to vote in South Africa and are planning to return to South Africa in time for the elections on 27 October 2021, you will not be able to vote in South Africa’s 2021 Municipal Elections.
Municipal or local government elections are, by their nature, about electing local representatives for the area in which you live in South Africa.
website: http://www.elections.org.za