Can confirm an identical issue is also present on my 6700 XT. Generic PnP driver is used, but neither Windows nor Adrenalin sees the display or lets me set a custom/appropriate resolution.
According to the 1280x400 LCD's docs (which are tailored for the Raspberry Pi) the HDMI timings appear to be:
hdmi_timings=
<h_active_pixels> 1280
<h_sync_polarity> 0
<h_front_porch> 64
<h_sync_pulse> 2
<h_back_porch> 18
<v_active_lines> 400
<v_sync_polarity> 0
<v_front_porch> 10
<v_sync_pulse> 3
<v_back_porch> 42
<v_sync_offset_a> 0
<v_sync_offset_b> 0
<pixel_rep> 0
<frame_rate> 60
<interlaced> 0
<pixel_freq> 37330000
<aspect_ratio> 3
![PhysicsDude_0-1697110794546.png PhysicsDude_0-1697110794546.png](/t5/image/serverpage/image-id/96716i162F82D7CACCDE99/image-size/medium?v=v2&px=400)
![PhysicsDude_1-1697110848143.png PhysicsDude_1-1697110848143.png](/t5/image/serverpage/image-id/96717i1E55D44B7DC1A5EA/image-size/medium?v=v2&px=400)