I've heard brains have a "plasticity" -- so they adapt to whatever activity you do most. I guess this makes me think that if you do more high-quality reading, your brain will naturally adapt.
My problem is I tried to increase my retention, which for me meant stopping and thinking about what I'd read. This obviously slowed down my words-per-minute -- but I do feel like I developed good recall. Maybe the trick is learning not to sacrifice one for the other.
About limiting distractions: I switched from reading on my Kindle to books. Having one dedicated hard copy of a single work which I'm committed to reading sort of "re-frames" the activity. Sometimes (before the pandemic) I'd go off someplace peaceful where there were trees and empty spaces, and then break out my book.
I also decided it was more important that I enjoy the act of reading every page than to focus on how many books I finished. Maybe another approach to your problem would be to re-visit your original question. I'm hope I'm not being dismissive here, but what is it that you're trying to accomplish with a higher WPM? (It seems like at least some of that could be accomplished by, for example, freeing up more time for reading, even at slower speeds.)