I wanted to try out guess access to a team. I've created a group first, then enabled the Team features. After that I invited my personal email address as a guest user.
I successfully received the Teams Invitation E-Mail. After downloading the Teams app (that was 1 day before yesterdays Teams announcement - if this has an relation).
When I log into the app I have to select the "Teams org", which says "Tenantname (Guest)". After selecting this the app switches to the Authenticator App with "help us kepp your device secure" ... "Enroll now".
Enroll Now opens the Safari Link to the Intune App Download.
Normal as long as your company has deployed CA/Intune policies that require this. In general, a Guest user will be subject to any such policy in both the home and the "target" tenant, however in your case that's a personal account so only the latter apply.