Any social platforms not focused on algorithms?

I think bluesky might fit what you're looking for, in the sense that either you can get chronological mode (the default feed), or use an recommendation algorithm of your own design.

It's called the #fediverse. Mastodon: https://joinmastodon.org Lemmy: https://join-lemmy.org Friendica: https://friendi.ca Pixelfed: https://pixelfed.org Peertube: https://joinpeertube.org

And many, many more.

Hackernews

4chan and imageboards in general

I find HN to be the best:

- Good UI

- No Algo, although ranking is a bit vague

- Discussion can go very deep as the limit of characters is large

Other than traditional forums, I don't think anything else beats HN. X and Mastodan and such are just too short, too quick.