Using Outlook for Android in business environments for email and scheduling
Workspace Booking?
Is your phone using Microsoft 365 Enterprise apps? Is that a Microsoft Teams icon in the bar at the top of the screen?
Your Enterprise Administrators might have control over this option in that case.
You are spot on!
I have two Android phones: Galaxy S20+ (private) and a Galaxy S10 (from work)
Both are running version 4.2048.4 of Outlook and my S10 doesn't have the "Use default browser" toggle and my S20 DOES have this toggle switch.