Hashtags exist for that purpose. You can follow them to be put into your home feed. As well, if you use the advanced web interface (like tweet deck), you can create a column with modifiers. Such as, I have a column that searches for both #pixelart and #lowpoly, but excludes posts with #NSFW or #Lewd, as well as #Pokemon (because I have a separate column for pokemon pixel artwork & lowpoly specifically)

I have heard misskey and calckey have a sort of trending feed, but not quite algorithmic, but unsure completely.

instead I want to see posts that fit my interests, regardless of who made them.

Follow hashtags then? I mean I’m following a good 40 or so people so far, largely newsy type things, but I’ve followed dozens and dozens of different hashtags so whatever gets posted with them pops up in my feed.

No need to go following Generic Mastodon User #374645 Who Likes Transformers™ when I can just follow #transformers to see my dumb robo pics lol

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.

that sounds more like you want a platform like this one, why do you want Mastodon to do that when you have Lemmy/kbin etc to access these kinds of posts?

however, you can make Lists on masto where you can add certain hashtags and it will give you a feed of posts with those tags, have you tried that?

You just posted on it

Like the others point out, Hashtags. However, on Kbin you can try the microblog which will show you microblogs from the communities you follow… which includes mastodon posts on the hashtags that relate to those communities.