I also imagine that neither configuring a few hundreds of routers in an industrial setting could be called a hobby. But I wouldn’t call myself an engineer for

I also imagine that neither configuring a few hundreds of routers in an industrial setting could be called a hobby. But I wouldn’t call myself an engineer for swapping a wheel on my car. But I would call myself an engineer if I were responsible for a small business making car wheels, even if we were not doing any R&D.