Does TOTP Work for users in a Secondary Directory via DA

Like many of our customers, a customer has a large external user community relying on their applications. We have about 7,000 external customers. Some are undoubtedly old customers, but 7,000 is a lot of people. Previously, I wrote about how to bulk add these people into your ID Vault, and that was all fine and good where we have only one names.nsf for everyone and everything. We may have had 2-3 servers in that org. Now, the 7,000 are in a secondary external names.nsf via DA (Directory Assistance). The Problem 1) How do you register and maintain the people in a secondary Directory? 2) Does the DA even work with TOTP?
This is a companion discussion topic for the original entry at https://blog.vanessabrooks.com/2024/08/sntt-does-totp-work-for-users-in.html