Having "information at your fingertips" really kills productivity for me. I need long stretches away from twitch reactions to "what's the capital of Uganda?" type of intrusive thoughts. I'd honestly pay for a "2 click" browser extension where you only get to make two clicks on any link per hour for a given domain on a blacklist of time sinks during certain hours.
Keep a small notebook beside you and promise yourself you are going to focus on the topic at hand for a period of time. When a thought, question or search topic pops into your brain, write it in the notebook. When you have some free time you can pick up the notebook at look up all those things. Of course, I often find that coming back to them they aren't all that important at all, and feeling of desperately needing to know has gone.
Otherwise, I try to create separate physical spaces for various tasks and try to practice mindfulness in general. It will always be an ongoing process though.
Here is more of a nuclear option that lets you micro manage your activity on an os-level. Unfortunately no Linux client afaik. A bit pricy, but very customizable and very effective: https://focusme.com