I can't find the ArcGIS app as an option when creating a new "tab" at the top of team channel? It would be great to have an online map appear and be viewable/searchable as its own tab within a particular team channel.
@DavidOutman - Totally agree with you. I too see a lot of value in that. This is something we are planning. We would like to release this capability in the near future following the 2021 User Conference.
Not sure if you ever resolved this issue, but what I have done is added a new tab to the Team, selected Website, then put in the URL for the maps and apps. I have tested this with AGOL maps, map apps built with Instant Apps, and with Experience Builder apps.