On the Teclast X98 Plus, the graphical framebuffer is upside down compared to the text framebuffer. When booting, the text shows up close to where the camera is, but when the graphical mode kicks in, the image appears upside down, compared to the text framebuffer and the EFI firmware logo. Note that while it is possible to rotate the device after a UI has showed up, it looks quite untidy. Let me know what debug data you need.
Please file new drm/i915 bugs at the freedesktop.org bugzilla: https://bugs.freedesktop.org/enter_bug.cgi?product=DRI&component=DRM/Intel