https://support.google.com/meet/answer/9303069
Under "Personal account users":
"Anyone who isn’t signed into a Google account can’t join your meetings."
This is a feature, not a bug: https://workspaceupdates.googleblog.com/2020/07/anonymous-us...
Although: "Note, this does not prevent users from dialing in by phone."
https://support.google.com/meet/answer/9303069