It is up to the source device to provide a name in a SPD (Source Product Description) Infoframe. If the player doesn't send it the Diva can't display a name.Received a appletv 2021 Friday. While I face lot of sync issue with tvos 14.5, upgrading to beta 14.7 fix most of them (except some <1sec random audio loss).
I assume that device is too new to be part of the diva edid database and be identified as AppleTV (the name field in Info tab / source is empty).
Please let me know if I can help there or when a new release will be available.