You maybe of the hook if you use Linux >= 5.7.
And it seem that you are of the hook if you are a member of the Open Invention Network (OIN).
But SEGGER's embOS is not based on Linux and their costumers a OEMs themselves. So their costumers would need to be OIN members or pay royalties to MS.
This is interesting, thanks. So the Linux kernel contains essentially non-free code that is, despite being under GPL, in effect not usable by others because of patents.