For historical reference, when the voting method was changed from “approval vote for up to 5 candidates” to “approval vote for as many as you want” in late 2019, it was done via a poll run here on Discuss.
That vote only garnered 33 total votes with a single one against. Though notably did not include an “no opinion - don’t count me” category so those who simply didn’t care aren’t represented any different from those who didn’t see the poll.
We already promote new committers (read also as: new voters) via vote here on Discuss.
If we want to be more formal in this process, Discuss still seems fine (IMNSHO), but we could do a direct email to all voters to reach out ahead of time to help ensure they see the poll, similar to what is done for the more formal SC election itself.