IR remote details are defined in device-tree and (no surprise) the N2 dtb defines the Odroid remote not the Dreambox one. It can be overriden in a custom IR map file (there's a wiki article on that).
The N2 dtb working proves there's no underlying kernel issue. The issue will be a difference between the actual hardware and how that hardware is currently described in device-tree. As the vendor kernel (which we have a device-tree file for) is rather different to the modern upstream kernel and I've never seen a Dreambox board we're reduced to guesswork and playing "spot the difference" with dtb files that work/don't-work. In this respect the N2 isn't so helpful as it isn't based on the W400 reference design and has a large number of differences.
To narrow the field, please try other "meson-g12b" device-tree files and flag if any have working audio?