Yes. I've been playing it for about a week and it is surprisingly good once you get past the simple tutorials. The online missions are deep even if you're the only one. The flight is credible and feels really smooth on my xubuntu desktop with Intel core 2 duo and Nvidia Quadro graphics. Two or 3 times I have had other players show up but I am not ready to tangle with experts yet so when I see others I just switch to a different mission lol. I fly the spitfire mostly cuz I always loved that plane and it seems to fly very close to what I expected.

Not LAC, but it's "dad" GL-117, yes. Flightgear was much better, (and today FG graphically curb-stomps LAC) but as a quick match against the CPU, it was fine.

Xonotic and Red Eclipse 2 began as quick, improved Q3A FPS clones and now they are pretty well known in lots of places with their mechanics being utterly ripped to set fakely placed as novelties and "revolutionary gameplays" into propietary AAA games.

Yes. I played it and I liked it. It reminded me very much of Aces High "classic" or its successor, Aces High 2.