DescentBB

I'm using flightgear right now, because it's free and runs on Linux.

What I really like to do, more than flying and landing (which are fun), is learning how to cold start these planes. Firing up the engines is really satisfying.

However, not all the planes have detailed cockpits and some of the switches aren't mapped out to do anything. I'm guessing a good flight sim would let you have access to more systems than this free game does. I'm not knocking flightgear, because it's actually great. I'm just wondering if there's something you use and recommend.

Some screenshots I took from flightgear:

Have you looked at X-Plane, Prepar3D or even MSFS 2020? The Linux version of MSFS only works on Steam and Prepar3D only runs on Windows, so that's a limitation if you hate Windows. X-Plane will run on Linux, but I'm not sure about the realism with it's add-ons planes. I know that in MSFS you can purchase add-on aircraft that have the ability to do prestart checks and actual startup from cold and dark. I have the next older version of MSFS and bought Aerosoft's PMDG 747 and 737. You can pretty much go through the routine of starting these planes from cold and dark and they're very close to realistic. I think they now have offerings for MSFS 2020. There are many others judging from the news I get from Flightsim.com as well, from prop planes to jets. I need to get back into MSFS since I've been busy lately. but I'd need one hell of a big hard drive to install it and the add-on planes, weather, terrain, etc.

https://www.prepar3d.com/

Also check out the wealth of information on Avsim's forums.

https://www.avsim.com/forums