Casting from iPad to Chromecast over VPN?`

[Chimaera 0]

I have Emby server running in a docker container on unRaid, working great.  I do not allow access to my server from the internet, so I set up Wireguard for my brother to be able to access Emby from his iPad from another location - this also works great.  However now he's trying to cast from his iPad to his TV (Chromecast 3) and it gets as far as Emby showing "ready to cast" on the TV then hangs.  I believe this is because Emby isn't really "casting" from the iPad, it's simply telling the TV where to find the media but that won't work because the Chromecast isn't connected to the VPN. 

Is there any way to actually cast from the iPad to the TV where the iPad receives the data then sends it to the TV?

[Luke 37053]

Quote

 believe this is because Emby isn't really "casting" from the iPad, it's simply telling the TV where to find the media but that won't work because the Chromecast isn't connected to the VPN. 

This is correct, yes, it does not go through the iPad.