Two things really help me:

1) acknowledging that deciding to watch a movie in the background, or be "kept company" by anything distractingly visual on a second screen, is a subconscious avoidance of the thing you aren't focussing on. Admit it, move on. In reality, I don't believe it is possible to work and watch a second screen. Work and listen to music or the radio? Yes, absolutely.

2) centralise your distractions. You're going to be distracted anyway, so as far as possible choose one thing to be distracted by; something that has its own inherent limits. If you're going to doom-scroll, try a set of interesting RSS feeds instead.