No variant rules unfortunately according to the Fdroid. You should check out the sudoku games from Cracking The Cryptic on the Google Play store if you want that. They aren’t FOSS but they have hundreds of handcrafted puzzles for a few bucks.
Your likely looking for the app “Puzzles” ob Android or one of its desktop versions, I am not entirely sure if they are actually open source but there are at least some people’s contributions and it not only has “Killer” sudoku but a whole bunch of additional options (as well as tons of other awesome puzzle/logic games)!
I played this in high school circa 2013. There was a server up 24/7 that hosted an infinite loop of the Venice map that always had the highest server pop. You’d occasionally find other servers going, or be able to host your own and get randoms, but more often than not, I played a TON of Venice for about a year. Good times.
From a quick video I saw, they seem similar indeed, but I haven’t played Thrive enough. I have only made it to a single-cell prokaryotic organism, lol (which is basically very close to the beginning of the game).
I would say yes and no. It is a game about evolution with some similarities but it is very focused on a realistic representation of evolution. This makes it a more complex game than spore and actively encourages many different niches not just agressive, peaceful and mixed as spore did.
Aldo currently they are working on finishong the cell stage and the beginning of the multicellular stage while have more in deapth discussion about the transition between the microscopic and macroscopic phases among other things.
The modding scene is (or, well, was) pretty active though, if you’re into that. There are still official te4 forums, but most folks hang out in the discord (yeah, I know.) including a couple old head modders that are pretty familiar with the codebase if you’re trying to do something exceptionally interesting with it.
VCMI - it’s re-written from scratch, open source, multiplatform Heroes 3 engine with many improvements and mods manager. It requires some files from the original game though.