@jana @MagicLike To be more specific: dGPU can work with specific Linux kernel versions but it was buggy as hell and thus disabled.
If your T480 has Nvidia dGPU, note that the intel GPU is also still present; Libreboot configures that, exclusively.
So, for Libreboot purposes, the Nvidia dGPU doesn't exist. On models that lack the dGPU, the same board is used but with an empty dGPU footprint. Might be useful for modboard adding 2nd nvme ssd!
https://libreboot.org/docs/install/t480.html
Info available there.