Backdated Meeting Attendance Report

Hi HotCakeX - jcgonzalezmartin is right.  Here's the key info from that https://support.microsoft.com/en-us/office/download-attendance-reports-in-teams-ae7cf170-530c-47d3-84c1-3aedac74d310:

During the meeting, select Show participants and choose Download attendee list.

There's another big issue with meeting attendance reports: the report only shows who was in the meeting while the organizer is there.  For example, let's say Fred is an organizer who joins a meeting a 9:15 AM.  Sally is an attendee who joins the meeting at 9:00 AM.

If Fred downloads the report before the meeting is over, then it will show that he joined at 9:15 and Sally joined at 9:15 AM.

Also, if Sally leaves the meeting (say 9:10 AM) before Fred joins, then Sally will not be included in the attendance report.

One further note: all of this applies to Teams meetings.  Teams Live Events have completely different reports and they work as you'd expect them to (complete attendance regardless of when the organizer joined, they can be downloaded after the meeting, etc.).