Mintou
I wouldnt say this is an issue XD if you are on a free OS, piracy is poorly often the only option to watch whatever you want.
Does Netflix etc. even still run on GrapheneOS? Spotify doesnt anymore, I think. At least recent versions dont start anymore.
Displaylink is not a huge issue I think, as the main issue is the proprietary driver that is normally not included in many Linux distros.
I wonder what displays and adapters Displaylink requires though.
I will likely not be able to use that phone with an external monitor.
And tbh, when I am outdoors, a phone is a great device, pretty big, totally fine for watching movies. For anything more, a mouse and keyboard would be needed, and probably better software.