Currently, when a domain is added to the org (for claiming managed accounts), there's no entry logged in the org-level audit log.

However, when a domain is removed. It's gets logged with information like this. With event type "domain_deleted" when checking with REST API.

[TimeStamp] [Location/IP] [Actor] Removed example.com domain

Output of Get list of event actions REST API suggests that there're event types "domain_verification_completed" and "domain_added"; but looks like they're not being used or exposed to org audit log.

Please add the event to org-audit log when a domain gets verified.