The nvgpu/tegra drivers are all open source and GPL (nvgpu for Tegra has been open source for a long time) but they were until recently on an old 4.19 kernel. The latest is 5.10. There's also the usual firmware binary blob stuff as everyone else. There are rumors about them working on mainline support for the Orin SOC, and Orin is (AFAIK) designed primarily to use UEFI as its boot mechanism. So it may be looking a lot better soon as far as full custom distros are concerned. The userspace is still all closed, however.
I suspect a lot of the push for upstreaming (and the original Tegra GPU drivers being GPL) is from their automotive/industrial customers who want continuity guarantees.
The hardware that was sold could still work perfectly fine instead of having to be trashed if only the existing drivers were recompiled, to run on a recent distribution.
