What do these commands report?
prime-select get-current
xrandr --listproviders
Just in case this is relevant to your situation…
https://www.reddit.com/r/openSUSE/comments/n5yfu3/nvidia_hdmi_sound_missing_after_driver/
This too perhaps…
https://wiki.archlinux.org/title/NVIDIA/Troubleshooting#No_audio_over_HDMI
I note for mxlinuix (where you note the HDMI is detected and you get sound) :
System: Host: <filter> Kernel: 4.19.0-16-amd64 x86_64 bits: 64 compiler: gcc v: 8.3.0
...
Distro: MX-19.4_x64 patito feo March 31 2021 base: Debian GNU/Linux 10 (buster)
....
Graphics: Device-1: Intel UHD Graphics 630 vendor: Acer Incorporated ALI **driver: i915 **v: kernel
bus ID: 00:02.0 chip ID: 8086:3e9b
and for openSUSE where you note HDMI is not detected, and hence you get no sound via HDMI I note:
Device-1: Intel CoffeeLake-H GT2 [UHD Graphics 630] vendor: Acer Incorporated ALI
**driver: i915** v: kernel bus-ID: 00:02.0 chip-ID: 8086:3e9b class-ID: 0300
So same driver is in use.
I recommend if you can’t get this working with any of the recommendations on this thread, that you write a bug report against the Tumbleweed kernel.
ILL HDMI port is linked to Nvidia chip.
OP tries to use device without drivers.