This issue is fixed in 6.6-rc3: 2de19022c5d7 ("drm/amd/display: fix the ability to use lower resolution modes on eDP")
It's backported to stable 6.5.6 as 79aec38ba852 ("drm/amd/display: fix the ability to use lower resolution modes on eDP").
Canonical needs to pull the fix into their kernel.
This issue is fixed in 6.6-rc3: 2de19022c5d7 ("drm/amd/display: fix the ability to use lower resolution modes on eDP")
It's backported to stable 6.5.6 as 79aec38ba852 ("drm/amd/display: fix the ability to use lower resolution modes on eDP").
Canonical needs to pull the fix into their kernel.