I have my own domain. I use FastMail for e-mail for my domain, and subsequently I frequently use the forwarded email alias tool when signing up for sites, resulting in a large amount of email addresses. If I purchase an API key for HIBP, would VaultWarden be able to search Breach Reports on each of the email addresses listed as a username, or would it only work for my VaultWarden email address?
I would suggest reading into the Help center article below.
https://bitwarden.com/help/reports/#data-breach-report-individual-vaults-only
According to this though it appears to search within vault items, aka masked email addresses for saved login items and not just your account email it seems.