I have never been able to force true concentration. I arrogantly proclaim that I have strong willpower* - I have very little trouble forcing myself to do something I entirely don't want to do, whether it be study, workout, code, whatever. However, forced concentration completely blocks off my ability to think fluidly, and I memorize very little from reading topics that aren't of interest to me (I am looking at you GC…
It seems like folks have their own way of learning how to concentrate effectively on things that may not immediately catch their attention. For me personally, it has been note-taking. Note taking seems to trigger a part of my brain that makes it think that the subject matter is worth paying attention too. Often my notes won’t be points but some doodles/diagrams to visualize what things look like.
Others have pointed out that certain kinds of prescription drugs are useful too, which... tbh I’m a little wary of trying. If they turn out to be too effective my internal logic system might have me using them all the time.