Hello!
Android 14 and 15 and Android TV 14 and 15 do not allow background activities;
Android 14 and 15 however do have "Always on VPN", unless deleted by the manufacturer;
Android TV 10, 11, 12, 13, 14 and 15 do not have "Always on VPN";
Android TV 10, 11, 12, 13 allow background activities.
Therefore:
on Android TV 14 and 15 the connection to a VPN during the device bootstrap remains impossible on an un-rooted device (*);
on Android 14 and 15 connection to a VPN during the bootstrap is possible in spite of the forbidden background activities, thanks to "Always on VPN";
on Android TV 10, 11, 12, 13, connection to a VPN during the bootstrap is possible in spite of lack of "Always on VPN" feature because background activities are allowed. However Eddie, unlike the other apps you mentioned, will not take advantage of it, due to a coded limitation according to which it doesn't let you configure app start at bootstrap if "Always on VPN" is not available on any Android TV 10 and higher versions and other specific Android versions. This is Eddie's part that needs to be re-designed and re-implemented in order to allow connection at boot on Android TV 10, 11, 12, and 13.
(*) Except maybe on specific devices for some manufacturer customization thru apps start managers at boot or anything else
Kind regards