MicrosoftBrian Reid C_the_S You only require licenses for users of your own organization, with a minimum of one license. All other users (that you could mark as guest user or external member in Entra ID) are not required to have a license! There is one other limitation: a guest to member ratio of 5:1. However, you may switch to monthly active users (MAU) using a subscription, where the first few users are actually free. I believe it's 50.000. Other benefit of attaching a subscription is that you become eligible for support.
What I find the downside, is that it's impossible to block access to all apps and only allow specific ones. For example the admin portals: if you only allow admin portals, access will be blocked because of some service principal AADIBIZAUX not being included in allowing access to the admin portals.
Unfortunately this service principal cannot be added to the allow list. Feedback from Microsoft is that it's a known issue with no known date of a fix.
