Are there any free and open source flight simulators for Linux that are fairly realistic (i.e. if I play one for a while, I will have some idea of how flying a real plane works)? The only "flight simulator" (if you can call it that) I've tried is the one in Wii Sports Resort; even with my very minimal understanding of flying, I know it is not done by tilting a Wii remote, and you should not fly inside volcanoes.
FlightGear Flight Simulator (often shortened to FlightGear or FGFS) is a free, open source multi-platform flight simulator developed by the FlightGear project since 1997.
David Murr started the project on April 8, 1996. The project had its first release in 1997 and continued in development. It has specific builds for a variety of operating systems including Microsoft Windows, macOS, Linux, IRIX, and Solaris. FlightGear is an atmospheric and orbital flight simulator used in aerospace research and industry. Its flight dynamics engine (JSBSim) is used in a 2015 NASA benchmark to judge new simulation code to the standards of the space industry.
I know it is not done by tilting a Wii remote
Actually, with FlightGear, you should be use Wii remote with a headtracking addon, to look around and/or point & manipulate cockpit controls. Linuxtrack supports it. Might need a bit of IR reflective tape or IR led.
Looking around and using it on the default C172P should look something a bit like this youtube video
that are fairly realistic
Jim NASA said FlightGear is as realistic as it can get [for an available space industry standard flight dynamics engine] - with better developed aircraft FDMs. Use the launcher to filter by FDM and Systems. Look at JSBSim planes especially, at the beginning.
Edit: looking at it, new user section of wiki has updated aircraft recommendations