It's been days (weeks?) and I'm still waiting for the option to appear for me. These "experiments" are super annoying when you are on what I'm assuming is the long tail of a rollout but the marketing/blog posts speak of the feature like it's already launched. If there's someone at Mozilla reading this: turn it on already! I want to get off Orion, it's so buggy, but the internet is unusable without an ad blocker.
As someone who successfully uses the internet day in and day out with zero ad blockers, this stance always amuses me. It's not hard to just ignore ads.