Bored at work and struggling to stay motivated

I've been in my current position for nearly 5 years. While I enjoy the subject matter, I've had a lot of responsibilities taken away from me over the past 2-3 years in an effort to better balance the workload on the team.

Now I'm bored. A temporary project might crop up here and there, but once they're done, I'm back to doing my own make- work projects that I come up with out of pure desperation. My manager is aware that I don't have much work and doesn't see any issue with it. It's been months. Meanwhile, I see that my colleagues are extremely busy, and I've tried offering to help, but there is very much a stay in your own lane attitude from both my manager and my colleagues.

I'm at a loss. I feel like I don't bring any real value to the team. It's soul crushing, and I have little motivation left to do the few remaining tasks I have bc they haven't been leading anywhere and my manager knows that.

I've tried looking for other positions, but very few groups are hiring right now. And for anyone about to suggest to do more training, trust me - it's one of those make work projects I've been doing. There is only so much more training I can handle.

Is this normal in the public service? Because it's my third time stuck in a position with little to no work. How do you cope?