How to use @mentions for user selection in Event history List Field but replace the built‑in @mention emails (Sites links in emails but not Tempo)?

I am using a!eventHistoryListField() with comments enabled and the mentionableUsers parameter so that users can @mention colleagues in record event history. 

However, in our production environment end users do not have access to Tempo at all. They only use Sites.

The problem:

• When a user is mentioned in the event history comments, Appian automatically sends the built‑in @mention notification email.
• The link in that system email takes them to Tempo → Record → Summary, not Site → Record → Summary.
• Since they have no Tempo access, clicking the link results in an error.
• We would like to keep the @mention search/picker behavior, but:
  • Either replace the built‑in @mention emails, or
  • Use the mentions only as a way to identify users and then send our own custom email with a Site-based record URL. ( with no automated emails)