I haven't see this as a problem, but I am working for a consumer network equipment semiconductor company. I haven't worked with graphics drivers which could be different. Normally we get the driver code from Cadence and Synopsys under a permissive license, it can be integrated in what ever you want. The documentation and especially the RTL is under strict NDA.

This driver code is often very self contained and does not use many or any Linux frameworks, it should be easy to integrate it into any operating system in any way. Normally you have to rewrite the driver code you get from Cadence and Synopsys to get it integrated in upstream Linux, because it does not meet the upstream Linux guidelines. This is a general problem with the out of tree drivers you get from the semiconductor industry.

There are also big players in the semiconductor industry which demand that every code inside the Linux kernel they ship has to be under GPL for legal compliance.

There is also not a single bad guy in the semiconductor industry which prevents upstream Linux support. Every player could do it, Google probably got most of the drivers in source for their Pixel phones and could have upstreamed them, but most of them probably need a rewrite. They could have offered Qualcomm some money to port support for the SoC used in a Pixel phone to a more recent major kernel version, I am pretty sure Qualcomm would have done it for the right amount of money.

How do they use the GPL2'd Linux kernel then? It implements drivers in the kernel and the license requires that the source be released. Do they use tricks like nvidia and create a free software shim module ties in a userspace driver?

NXP manages to do it fairly well though. Their chips have excellent upstream support.

Don't forget foreign actors constantly looking to steal designs. If government properly enforced IP laws and imposed sanctions on countries violating them then we wouldn't be in so much mess.