It’s really frustrating when something you were able to do on an older model vehicle is taken away in a newer model. I had a 2016 Yukon that allowed me to have my phone connected to carplay, but I was able to use my iPad for audio. On my 2022 Yukon, it doesn’t recognize the iPad as a device at all, just as you’re describing. I had a service appointment today and I asked them to look at this. They weren’t able to come up with a solution.
I tried what another user suggested and disabled Siri. That didn’t help. I’m also using an apple cable, and my iPad is updated with the latest software. Also, my husband has a brand new iPad and it also doesn’t connect. Hopefully GM comes up with a software patch, but I doubt this is seen as an issue.
So, perhaps give this a shot, just to determine if there is a way at all...
Place your phone in Airplane mode or power it down completely before you turn on your vehicle.
Power up your ride...let everything boot nicely.
Plug in your iPad...see if it connects as a media player (Select USB for audio input on the audio sources screen).
If that doesn't work, try pairing your iPad w/ Bluetooth, then select Bluetooth as the audio source from the sources screen.
Now, I have an interesting question...presumably you can have the same audio source/tracks/app/etc on your iPhone as you do on your iPad (Apple syncs them in the cloud)...so...why not just use CarPlay on your phone for audio?
I am an Apple Music subscriber, and can listen to all of iTunes library on my Mac, Apple Watch, iPhone, iPad, AppleTV, etc..I realize this is not your actual question, nor is everyone an Apple Music subscriber, but even if you were Spotify, AmazonMusic, YouTube Music, etc, the same app will run on your iPhone or your iPad. If you have a bunch of mp3's or aac's downloaded to your iPad, you can easlliy move them to your phone by syncing w/ Apple Music app on a computer...or you could move them to a USB stick and plug that in the USB port?
Again, I realize the latter part of this post is not what you asked...but could be an option for solving this a different way.
I have an iPad, I will play w/ it when I get a minute...
To be clear, you want to be able to connect via CarPlay (wirelessly) w/ a phone, and use your iPad as a USB connected media player (in iPod mode?)
Have you tried the opposite...connect phone via USB for car play (wired), and pair your iPad via Bluetooth as a bluetooth Audio Source?
UPDATE:
Got ahead of myself...didn't re-read OP's question...
OP wants Video playing on iPad screen with audio going to vehicle speakers...preferably NOT using Bluetooth...so my questions in the 2nd and 3rd paragraph is not worth asking or answering..sorry all.