Ditto, with vanilla settings. But I had to temporarily disable additional postfix rule
POSTCONF_smtpd_client_restrictions: 'regexp:/etc/postfix/shared/client_access_regex'
which worked perfectly before the upgrade (uses regex rules to reject spammers). The real issue is that with this setting enabled, postfix starts rejecting all incoming email, but I can’t see why from the logs!
A while maybe, but it’s been hours and still nothing in logs (neither accepted nor rejected emails are shown, and there is inbound traffic).