As of February 2024, Outlook Mobile now supports the Signature 365 add-in on both Android and iOS devices.
There are a number of pre-requisites to this being enabled and visible within Outlook Mobile, these are detailed below.
Native mail clients such as Apple Mail or Gmail cannot support the Signature 365 add-in, you will need to user server-side injection for these clients
You will need to ensure that specific versions or later of Outlook Mobile and the Signature 365 add-in are in use in order to use this feature.
Outlook for iOS - v220.127.116.11
Outlook for Android - v4.2402
Signature 365 Add-in - v1.8