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KSP's spiritual successor Kitten Space Agency just released a free public pre-alpha
(www.youtube.com)
https://ahwoo.com/store/KPbAA1Au/kitten-space-agency
You can zoom out from a craft to the solar sytem and beyond (interstellar is on the roadmap), and it's completely smooth and seamless 
Also, I love the cat theme, but I'm very divided if I can ever stomach launching a mission with a crew based on my IRL cats 
I've played it for about an hour (on Windows) and didn't experience any crashes. Honestly the experience was mostly seamless. At one point, an error message popped up but it had no effect. Terrain colliders are not well lined up with the terrain mesh, but that is to be expected when creating terrain for literally the entire solar system. Experienced some minor graphical glitching deep in the atmosphere of Jupiter. That's really all the problems I had.
As far as tech demos go, I think it's really promising. The amount of info panels there are, the manoeuvre calculators, it's all way more than stock KSP already. The solar system is all there, it's impressively fleshed out.
The (secret) in-game craft builder is basically non functional but it's almost in a functional state, you can see the promise, and you can see why they hid it.
Overall, it's really not far from a minimum viable product, like a playable game, similar to KSP in its alpha, but way prettier. I maxed out the settings on my RTX 3080 Ti and my fps was pegged at 60 the whole time.