Can’t output 4k video and 5.1 audio from an iPad Pro

I have an iPad Pro 2018 model (11 inch) which I’m connecting to my Samsung Q6FN tv (55 inch) with a HDMI cable and a USB-C to HDMI adapter. The adapter I’m using is the Satechi Aluminum Type-C to HDMI 4K 60Hz (ST-TC4KHAS). The cable I’m using is a cable that supports 4k at 60Hz (this one, bought from a swedish online store.).

I can’t get Infuse videos to play in 4k and also, I can’t get the iPad to output 5.1 audio. It only outputs stereo audio from Infuse.

The TV is connected to my Pioneer VSX-922 receiver with a HDMI cable.

In the iPad OS settings, under the ”Display & Brightness” category I have activated the option ”Allow Display Mode Changes”. In Infuse, I have the ”5.1 audio over HDMI” activated. When playing the 4k video I’ve gone in to the ”External screen resolution” setting and the options for 3840x2160 and 4096x2160 shows up. When I select any of the two, the check mark shows for about a second and then disappears. It doesn’t even default to any other resolution (not even 1920x1080, which is the playback resolution on the TV). Just disappears.

I have tried playing 4k material from other apps on my iPad, like YouTube (works just fine) and Netflix (works just fine, and plays 5.1 audio as well).

Does anybody have some kind of solution? What can I try to get this to work?