It is necessary to connect the Raspberry and the Baglebone by LAN in the same network. Through Wi-Fi, have access to manage these devices (ideally through wpa_suplicant (client)). Through the hotspot is also possible but less preferable.
I can’t find a solution for dietpi.
On openWrt I can do it without problems.
As stated above, our script don’t offer the possibility to create a bridge network device. This would need to be done manually. There should be plenty of guides on the web how to do it using ifupdown