Hmm, not sure that boredom is the underlying problem here. I pretty much never get bored by myself (I really enjoy thinking, daydreaming, or making stuff), but I put off unpleasant tasks probably as much as you do.

So maybe these are two separate problems. For getting less addicted to mindless online content, I think you can pretty easily train yourself to daydream more, or consume "healthier" content (books, music) or create something yourself (intellectual or artistic). These habits really stick. But for unpleasant tasks I'm not sure if making the habit is possible, I'm as stumped as you.

Meditation isn't supposed to make the pain go away, it's supposed to train you to suffer less from the pain. So for meditation the idea would just be to make it a game of seeing if you can train to do it longer and better despite the averse feelings, and learn to detach from the feelings. But if your internal motivation is toast, that might be hard to make happen. You might try seeing an actual meditation teacher about this.

The point where you have started the task and then get bored and stop sounds like the key point here. Can you try focusing (maybe in the sense of Gendlin's focusing) on what goes on in detail with your mind, the task and how you're conceptualizing working on the task right now and in the future? My experience is that I can procrastinate on starting a task but when I do start it, if it's something like housework I've done it hundreds of times before and can go on autopilot.

I guess it's mostly housework-like autopilotable stuff for me now. After 20 years of trying I threw in the towel on getting myself to do stuff that's difficult, I don't really want to do, and not doing it won't literally get me killed, which pretty much crashed the whole studying-and-employment pipeline.