Are there testable demos for alternative game engines?

Hello everyone.

I am getting interest in alternative game engines like Open3D Engine, Godot, Flax, Stride, Bevy, etc...
But I'm surprised how hard it is to find any "playable" demos of these. The only things I was able to find were screenshots and videos, but no proper executable that shows off their performance...
Do you know any demo for any alternative engine (by alternative, I mean, not Unreal or Unity) ?

Thank you :-)
(this is my first post on an ActivityPub community, sorry if I didn't post it the right way)

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