I have not found any serious alternatives. The main problem is the chicken and egg problem where no one cares unless other people are using it. I created my own alternative as a side project (https://zsync.xyz) with some differences (eg. tags instead of subreddits), but there are no users - and why should there be?

I used to use Reddit pretty heavily, but I stopped when I realized outside a few small use cases it wasn't benefitting my life and was mostly a time sink. I find that HN and Twitter is enough for my "social media" needs.

I do hope we see a better alternative to Reddit though, one focused on fostering high quality. Reddit was like that in 2008-9 when I joined, but in just a few years devolved into the meme dumpster and PC hivemind. The Reddit founders and their investors (cough YC *cough) should be embarrassed. It's like raising a child prodigy with the potential to cure cancer only for that kid to grow up into some grifting alcoholic bum who just smokes weed all day and survives off of fake disability benefits.