Part of the graphical booting process is a handover from early-boot drivers (simpledrm) to the device's native driver (amdgpu, i915, etc). We should double-check that plymouth get's the handover right. This used to be a problem with early-boot fbdev graphics, because the fbdev code didn't support it well. DRM's simpledrm supports hot-unplug before the native driver takes over. That would resolve the issue, but one never knows.