MC250343 – Your end users will soon be able to add and remove delegates from within Outlook for iOS and Outlook for Android. Delegates will be able to access those mailboxes on their mobile app as well. This message is associated with Microsoft 365 Roadmap ID 67273 and 67274. Rollout begins in late April and should be complete in early May.
Link: Outlook mobile clients will soon provide access to delegate mailboxes