I don’t know, but it could be interesting to try. I could easily imagine topic-focussed servers that go into more depth on specific topics. Perhaps you would only federate things that are at a high level, or directly linked. Kinda like a wiki, but with each community doing it’s own decentralised curation and moderation…

I haven’t seen any spam on Lemmy yet, and only a tiny amount on mastodon (I’m much more active there).

Man, their website is pretty off-putting. Where’s the get-started/dive-in type page? How do I use the thing?

You can do that with NoScript too. Is the Umatrix UI any better, or are there other benefits?

Nope. Died like Digg and a bunch of others. There’s a run down here (which I only quickly skimmed): https://productmint.com/what-happened-to-stumbleupon/

What would be really cool would be an open source, federated version of DMOZ

Yeah! StumbleUpon was cool. Something about how it tried to engender serendipity.

Such a pity that so many other good recommendation engines died or succumbed to enshittification.