And now there's a new cause of this bug. If I simplify the framebuffer drivers installed in initrd then it causes i915 to take 10 seconds to start, whereas Plymouth stopped waiting for it at the 8 second mark and so fell back to using SimpleDRM.
And now there's a new cause of this bug. If I simplify the framebuffer drivers installed in initrd then it causes i915 to take 10 seconds to start, whereas Plymouth stopped waiting for it at the 8 second mark and so fell back to using SimpleDRM.