If you're talking about the Mini 3 Pro DJI RC controller with the built-in screen, no it will not work because both USB-C ports are not capable of outputting video. However, the DJI RC PRO does output video & you can use your BT-300 glasses with the use of the BT-35e HDMI Interface Box. Hopefully, in the not too distant future, DJI will issue a firmware update to make the DJI RC Pro compatible with the Mini 3 Pro.
OP is asking if DJI RC smart controller (with screen) that comes with the Mini 3 Pro works with BT-40. Unfortunately it does not because none of the controller’s USB-C ports output video.
@sapsan is trying to say the BT-40 does work with the RC Pro, whose USB-C port supposedly outputs supported video for the Movario BT-40. Still verifying that. BT-40 arriving tomorrow!
Update: RC Pro works with the BT-40, but the DJI RC does not. No lag at all, because it is hardwired through the USB-C charging port, which also outputs the necessary supported video, in a complete replication of the internal RC Pro screen with telemetry, which cannot be removed.
Neither the RC Pro nor the DJI RC have any casting utility. The RC Pro has a mini HDMI out and video on the USB-C. The DJI RC offers neither at this time, but has one port labelled "HOST" which is not recognized by the Moverio BT-40 glasses. It theoretically might have some future support for output.
