Some more good advice:

Turn off your YouTube watch history. This disables video suggestions when you open the website or the app.

The internet is a rich tapestry of human knowledge and experience. When I scroll Instagram, I often discover incredible new artists who present in human form. Once you start tapping like on things, the journey of discovery is almost biblical.

The secret is learning to use your tools to bring joyful moments of surrender into your otherwise mundane existence.

Putting in blockers and the like helps, but what I've found worked best was to consider this quote by Anthony DeMello:

"When you fight something, you're tied to it forever. As long as you're fighting it, you’re giving it power."

When I learned to stop feeling bad/guilty/thinking this was a problem to solve and just let my mind drift, I found that my mind naturally learned when it was disciplined work time vs. browse the internet time. Personally, I noticed that when I didn't have any artificial restriction, I was less inclined to waste time on those things.

In practice: "oh, my mind doesn't want to do that other thing right now but it does want to go look at this thing; let it." The more I've loosened my grip, the less distractions have affected my productivity.

If you've got an iPhone/Mac I recommend Apple's free Apple Configurator tool to lock down your phone to only the set of apps you whitelist and/or route all traffic through a VPN/Proxy that whitelists only certain IPs. You can only change the whitelist when you're physically back at your Mac so prevents me impulsively relaxing the restrictions in any moments of boredom.