Support custom screen resolution on nvidia opensource drivers (nouveau and NVK)

[ralencode]

i have nvidia rtx 3060 and i mostly use opensource driver in mesa. lack of this feature (and ofc Xwayland but its manageable i guess) stops me from stwitching from Hyprland to niri: i have 5120x1440@120 monitor, but the highest resolution available on niri is 3840x1080, and everything is pretty blurry. i dont want to switch to proprietary driver full-time

[YaLTeR]

Does niri msg outputs also only show up to 3840x1080? Do you have to use a custom modeline in other compositors too like sway or GNOME?