Backup Client and any other automated users.
If you're using the Bitbucket Server's Backup Client (or any other automated scripting utilities that consumes the rest api) - you will want to create a dedicated group for these users (we recommend a group named 2fa-excluded-users). Then in the Rules configuration, add in a "Allow" rule for any path starting with / and the group is "2fa-excluded-users". This will allow the user to be excluded from the 2FA requirements.