Anyone know if a client comparison table exists? That would be really helpful.
Currently I'm wondering if the Teams web app is set to 'anonymous' access or if it needs an MS account for guests?
People can join your meetings using either the web app, or any of the other apps, without any kind of login.
To join a team as a guest, to see it's channels and files, then some kind of account will be needed. This could be an organisations account in another tenant, or a Microsoft Account.