We have a very active small group within the +8 to +12 zones (AU / NZ) usually running flight plans and short flights as groups, 30 mins to 2 hours.
Also into some bush planes and a bit of mucking around.
If you are interested Discord is: https://discord.gg/35MT63U
From my understanding, This will be possible (To fly in groups cross platform, ie MSFS for XBox and MSFS for Windows) with the Xbox Group service.
If you were to make an “MSFS ANZ” group, Anyone can join, again, whether on MSFS/XBOX or MSFS/Windows and see each other.
As mentioned before - The XBOX Clubs/Groups thing is quite new to me.
I did find this as some light reading - Wasn’t able to find anything specific from Microsoft that referenced cross-platform support though in my quick search.