When to inform a user that an app requires touch ID for certain actions?

We are building an app that is financial in nature and as per client requirement, there are certain actions that 'touch id or face id' is required to proceed. Therefore, users who are using phones that are not Touch ID-capable cannot do those functions.

My question is, when should we start informing the users that certain actions require Touch ID?

Also, should we even display to them those actions or do we just hide them if the app detects that their phone is not Touch ID-capable?

I see this as a double-edged sword though because on one hand, it's less frustrating for them to just don't see the action buttons if they aren't able to use them anyway. On the other hand, they wouldn't know that those functions actually exist, just that they're using a very old phone hence those functions are disabled for them.

How should I approach this?