FYI: The onboarding for this forum was inordinately difficult and took about 45 minutes.
It seems there's something about the confirmation email configuration that is incompatible with the iCloud+ Hide My Email feature. Emails come through apparently without any sender email address, causing them to encounter an error in Cloudflare.
This affects both the Discourse and Zulip confirmation emails.
As a separate bug, trying to switch to a different email address during the confirmation process after the first one failed also didn't work: it produced an error saying "An error occurred: You are not permitted to view the requested resource."
I ended up with two separate accounts as a result, one of them not properly activated.
Even after making my account, I still can't change my email because it still requires a non-receivable confirmation email.
Moreover, this struggle was completely unnecessary, as I have zero need for receiving email notifications from this forum anyway!
Please make the email field optional.
Thanks.