Sorry Pauli2485 for not reading your comment closely enough. The config you mentioned - MF3 + ExO P1 + M365 Apps for Devices is supported for classic Outlook today. Nothing is changing with classic Outlook licensing.
I still don't understand this setup. Adding 5 users to classic Outlook on one device, where each user can see the others data and emails feels very problematic and a data privacy/security nightmare. Though it is supported.
The goal is that the new Outlook licensing will match that of the classic Outlook. We just don't have every case covered as we're still in preview. The new Outlook does support MF3 + ExO P1 + M365 Apps for Business/Enterprise. Just that the new Outlook doesn't currently recognize the Device based licensing for those M365 apps as it isn't tied to a user account. We'll definitely look to support that in the future. Feel free to add to our feedback portal, so we can better prioritize this setup. Outlook ยท Community (microsoft.com)