My hunch is that it has nothing to do with the screen. It's the device that's the problem, reading on a device that you can theoretically do anything from watch

My hunch is that it has nothing to do with the screen. It's the device that's the problem, reading on a device that you can theoretically do anything from watch porn to build a business to doom scrolling facebook. When I'm on a computer my brain knows I could check some attention stealing thing so I get the idea in my head, interrupting my attention. When I switch to a kindle or a physical book I can feel those impulses to divert my attention for the first minute, but they dissipate quickly when my brain realizes I'm not on a computer. Then my brain stops trying to interrupt itself, hunting for some dopamine shot.