As a result, our instance https://lemmy.dbzer0.com/ got 625 new user registrations (of which 536 where accepted) in the past 24 hours! And the registrations are not abating even now. We still get like 10 new ones per hour!
I suspect this is probably the largest advertisement, for lemmy specifically, since the main reddit blackouts 1.5 years ago.
Have your own instances also seen an influx of new users?
Captcha and email verification are trivially defeated by bots. If just getting lurkers is a concern, try using a registration application form like we do. Do you at least see these lurkers as MAU? (i.e. just voting)