Nowhere in the GPL does it say how you can USE the software - you are free to run, modify, and use it any way you see fit. All its restrictions are triggered by DISTRIBUTION of the software, especially modified versions.
[0] https://en.wikipedia.org/wiki/OpenWrt (see History section)
For most physical objects and concepts, distribution isn’t a subset of use. e.g. the post office. You can be a user, but you have no ability to distribute the post office - because that’s not a thing that is possible or makes sense. In that case distribution is not a subset of use. Other examples: most saas, e.g. gmail. Good luck distributing gmail.