I’ve been using a Dell XPS 15 with Pop!_OS for three months now — after 30 years of macOS — and I don’t really have issues with integrated/discrete graphics switching.
When on the go, I switch to Intel graphics and I easily manage to get 6–7 hours of battery life, even when doing 3D modeling and CAD work.
Then when I’m home, I switch to Nvidia graphics and have my machine closed and plugged in with an external display. So battery life doesn’t really matter. But I tested it a few times and got about 3-4h, depending on the load of course.
It would have been nice not to have to reboot for switching, that’s true. But it only takes a minute. And since I only use integrated graphics outside of the office, the need for an external monitor is zero to none.