lkiredshaMy client is a Mac Mini M1, my monitor is a LG UltraWide 49WL95C-W 49" (resolution is 5120 x 2880).
I only have up to 1080P and when I go to NVIDIA settings the option to add a custom screen resolution is greyed out.
in shadow client app, my monitor is detected as Goldstar Company LG HDR DQHD, 192X1080 (tried both production and alpha version)
in MacOs (host) here is my resolution, as expected
Update, 3840x1080 seems to be the max settings when disabling Always match Shadow resolution with local display » in Video & Display -> Video