Here, people can write post related to any game engine (NOT on commercial level [e.g. Epic Games Store bribing companies], just on technical or information level [e.g. how does an engine work? or what will source 2 look like]). You can even talk about hhyyrylainen’s game engine “Leviathan” in this thread (you can talk about it too, @hhyyrylainen :-]). It is also accepted to talk about programming a game engine from scratch. As long as it’s neutrally related to game engines, it’s ok to talk about it.
I’m starting this post with a video about Valve’s Source 2 physics engine: Rubikon.
Note: Be careful, the video seems to bugged. It can stop at any time with an error. At least, that’s what just happened to me at 2:46 and a bit later too. Maybe it was just because it’s raining hard outside.