It's definitely not a complete nor perfect solution, but I've noticed that a number of accounts disproportionately post very negative news links. I've started blocking some of those users. It helps break it up a bit. I'm sure I'm missing some news now, but there's only so many times I can see posts about the world burning up or genocide before browsing lemmy becomes stressful and nihilistic.

So if I see the same negative news story on multiple communities, I'll click on the user and if they're blasting negative stories everywhere I just block them. For example, I just blocked silence7@slrpnk.net, not because of any harassment or anything, it's just that they almost exclusively post political and climate doomsday stuff.