[MM3-users] Easy way to integrate captcha/reduce subscription spam?

Dear all,

my mailman3 instance is flooded with subscription spam, yet I haven't found any canonical method of integrating a captcha in to the subscription form. Is there really none at all? Perplexity.ai says I should install the python package django-simple-captcha but is unclear about the steps needed to actually make the captcha appear.

Are there other ways? Is there any method that is robust and survives upgrades?

Also, would there be a way of batch-deleting all those thousands of spam registrations that have accumulated (what they have in common is that their email is unconfirmed)

Thanks in advance for any suggestion!

Johannes