Alright, here's a list of some stuff I've found. Haven't played all though.
The closest in gameplay and theme to Strive:
The classics:
Slave Maker: Pretty much inspired a lot of games in the genre, focuses mostly on slave training rather than managing a lot of different kinds of slaves from what I remember
Jack-o-nine-tails: Inspired by Slave Maker, quite similar, but more fleshed out and if you play the version before 2.0, it had quite a high skill ceiling with its complex slave training system. I've heard 2.0 and later made it quite a bit easier, but I don't know whether that was for the better or not. Art is from art packs, not commissioned for the game specifically.
The derivatives (possibly):
Brothel King: Very similar to Strive from what I can tell, only played the beginning. Randomized slaves. Art is from art packs, not commissioned for the game specifically.
Whoremaster: Same as Brothel King. Randomized slaves. Art is from art packs, not commissioned for the game specifically.
No Haven: Adventure/management sim of a slaver band. Randomized slaves. Art is being commission continuously, which can be seen here:
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.
Simbro: A bit different from the rest, I think. Also abandoned. But seems good.
Stationmaster: A 3D slave management game where you build a space station for prostitution/entertainment.
Strumpets: A slave/whore management game with its own art/animations.
Free Cities: You build a whole arcology/city in a post-apocalyptic future as its ruler, with extensive control over the slaver future culture you choose, such as Roman inspired or Hedonism. It has some extreme content, so be warned, even more so than some of the other mentioned here. The F95 version is not the latest; the latest is the pregmod version, which doesnt just focus on pregnancy but generally continues the game development. The game repository is here:
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, and here is a thread for info, but remember that these threads are constantly moved/deleted:
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There are art packs, but the art isnt taken from the internet, rather vector/raster image "dolls" that change with different attributes.
90 Seconds Slave: A slave management/trainer game in 3D.
Similar to Strive in theme:
Harem Collector: A pretty light-hearted adventure RPG maker game where you "collect" harem slavegirls of various backgrounds. They are used in your party in combat and have various abilities, similar to Strive. It's less of a management game though and is focused on the relationship with your slavegirls. A lot of the art for the different scenes is placeholder 3D, but replacements are actively being commissioned from 2D artists.
Harem Hotel: A really popular game in the same vein as Harem Collector, but in Ren'Py. You have a large harem of various girls you build relationships with and train. 3D art made for the game specifically.
Edit: Another game that I couldn't find a thread for is My Slave Brothel, a real time slave brothe l manager where you build the physical brothel and buy slaves. Only found it here:
https://f95zone.to/threads/best-brothel-games.19591/#post-2670665