While the discussion here is not yet finished it seems like there is some support for requiring emails for requesting wikis but also some opposition. Based on one query [1] it appears that there are 2630 verified emails for 4639 approved wikis. This makes me agree with some of the opposition and therefore I'd suggest we first start by providing for a notice/warning to users and consider a requirement at a later time if numbers improve and if we see that users are willing to provide an email if they are warned. This is what I'd propose

• When creating an account and not specifying an email, there would be a dialogue that would say: "Are you sure you don't want to specify an email? If you lose your password you will be unable to recover it"
• When requesting a wiki and not having an verified (or unverified) email, there would be a dialogue that would say: "Are you sure you want to request a wiki without having a verified email? If you lose your password you will lose access to your account and wiki."
• Implement a way of being able to get statistics of how many users go back and add an email or abandon the process altogether

If the one on Special:CreateAccount isn't possible, at least have the second one. Same for if statistics are too hard

[1]

SELECT COUNT(*) as approved_wikis
    ,COUNT(DISTINCT cw_dbname) as UNIQUE_APPROVED_DBs
    ,SUM(CASE WHEN u.user_email_authenticated IS NOT NULL THEN 1 ELSE 0 END) AS approvals_w_verified_emails
FROM metawiki.cw_requests r
LEFT JOIN metawiki.user u on u.user_id = r.cw_user
WHERE LOWER(r.cw_status) = 'approved'
AND YEAR(r.cw_timestamp)=2022