I tend to like games that have lots of "levers" to play with and spend time figuring out, so I think that tends to be the unifying factor in the above games.

I don't know of anything really comparable to Oxygen Not Included in terms of all the physics and stuff. I'd like something like it too (especially since Tencent bought ONI and now has some locked graphics for some in-game items that you can only get by enabling data-harvesting and then playing the game for a given amount of time, which I'm not willing to do. They don't have an option to just buy that content. At least it's optional.)

For Rimworld and Oygen Not Included, both are real-time colony sims. Of those, the closest stuff on my list is probably:

• Dwarf Fortress (note that the commercial Steam build looks quite different from the classic version, has graphics and a mouse-oriented UI and revamped the UI and such, which may-or-may-not matter to you; if the learning curve being steep is an issue, that makes it a tad gentler). Rimworld is, in many ways, a simplified Dwarf Fortress in a sci-fi setting and without a Z-axis.

• Kenshi. Not a colony sim. You control a free-roaming squad (or squads) in an post-apocalyptic open world. That's actually a bit like Rimworld. However, you can set up one or more outposts and set up automated production there. It's getting a bit long in the tooth, and the early game is very difficult, as your character is weak and outclassed by almost everything. Focus is more on the characters, and less on the outpost-building -- that's more of a late-game goal. I find it to be pretty easy to go back and play more of. There's a sequel in the works that'll hopefully look prettier. Not really any other game I'm aware of in quite the same genre.

The other things on my list don't really deal with building.

Oxygen Not Included has automated production. If you're willing to go outside "colony sim", there is a genre of "factory-building games" where one controls maybe a single character or base element and just tries to create a world of automated production stuff, maybe with tower defense elements. I'd probably recommend Satisfactory if you want 3D and a first-person view. I like it, but in my book, it doesn't really compare with the games that I've racked up a ton of time on, winds up feeling a bit samey after a while, looks like I have thirty-some hours. Mindustry is a free and open-source factory builder that you can grab off F-Droid for Android to play on-the-go; that and Shattered Pixel Dungeon are probably my open-source Android favorite games. Dyson Sphere Program has outstanding ratings, but I have not gotten around to playing it.

There are a few colony sim games sort of like Rimworld or Dwarf Fortress. I tried them, and none of them grabbed me as well as they did, but if you want to look at them:

• Rise to Ruins is a colony sim does have combat, but less focus on individual characters than Rimworld. I don't like it mostly because the game is not really designed to be winnable, which I find frustrating. There's growing "corruption" coming in from the edges of the map, and the aim is to try to last as long as possible before becoming overwhelmed; you can flee it to other colonies. Technically, there are some ways to defeat the corruption, but not really how the game is intended to be played.

• Prison Architect. This has somewhat-similar graphics to Rimworld. You build and manage a prison. It's not a bad game, but it doesn't really have the open-world scope of Rimworld.

• Timberborn. This was in fairly Early Access the last time I spent much time on it, so I'm kind of out-of-date, and it looks like it's still in EA. Doesn't have the combat elements from Rimworld or Dwarf Fortress.

• Gnomoria is kind of like a much-simplified Dwarf Fortress. It didn't really grab me, but maybe it's your cup of tea.

• Klei, the guys who developed Oxygen Not Included, are currently working on a new 3D colony sim called Mind over Magic. I have not played it, but if you're desperate for more ONI and like colony sims, might be worth investigating.

I'm right there with you. I absolutely hate Paradox's DLC policy and I'm guessing they lose a ton of paying clients the moment they hit the store page and get a 200-500€ price tag for the full experience, or even over 100€ for just the best hits for a really old game. I know they have mouths to feed, but i really don't like the way they do it and how they abuse their position of niche games nobody else makes. Nevertheless, even though you may choose not to purchase their expansions, you still have extremely healthy modding communities to carry you over.

Still, i wasn't coming so much from the angle that it's a smaller company providing better value than larger companies, rather showing to the OP that there are non multiplayer games that easily can provide over 500 hours of entertainment regarding the slighly off topic matter presented on the latter part of their comment. Of note is the fact that they don't use grinding mechanics to do it, for the most part (x series can be a little grindy in some aspects, but not overly), which is the mark of how incompetent devs try to get more "entertainment" hours out of their games.