Using Outlook for Android in business environments for email and scheduling
I found that screen (under "Default Apps"), thanks for the pointer. It looks like all the 3rd-party apps I'm having issues with (Outlook embedded browser not redirecting) are set properly to open their own native links - presume Outlook browser is just ignoring that?!
Interestingly, Chrome is set to "Don't open supporting links" but when I click through any options to change this are greyed-out.