Reddit Migration

As a point of pedantry, "show posts in timestamped order" and "show posts ordered by vote popularity" are both algorithms. Algorithm doesn't have to mean "mysterious and nefarious Facebook feed magic". However posts get picked and sorted for your feed, that's the algorithm... even if it's as simple as "pick random posts". You got at a better name at the end of your post which is personalized recommendations. They typically require fairly exotic analysis pipelines that are much more computationally (and consequently financially) expensive to run than feed generation algorithms that are powered by the global/shared sorting criteria that are popular in the Fediverse.

But as others have noted:

• Mastodon uses a people-focused approach. If you want a topic-focused approach... you found it in Lemmy. Sub to topic-based communities here.
• Mastodon does have hashtags to represent topics, and those can be subscribed to just like people. Hashtags don't have moderation teams to keep them on-topic though, so it can be a bit of a grab-bag of content. I find the result inferior to Lemmy, personally.

By curating your list of Lemmy communities or Mastodon hashtags, you can create a topic-oriented feed that caters to your interest. Tag/community discovery takes more work than a recommendation engine that tosses ideas your way autonomously, but also gives you more control. Either way, I don't think you'll find systems in the Fediverse that do personalized recommendations. In addition to the ideological opposition to them, they're very complex and pricey which puts them a bit at-odds with volunteer run/funded infrastructure.