If you've got a beefy enough PC you could give fs2020 a go. It's currently on xbox gamepass for Windows and they do a 3 month trial for £1. It's a fantastic game and very pretty to look at, but as someone else has already mentioned it can be a bit boring just flying from A to B, unless you are really interested in civilian planes.
For WW2 sims the IL2 series is the gold standard, starting with Battle for Stalingrad, then Battle for Moscow, Battle of Kuban and the latest one Operation Bodenplatte. For WW1 kites the same team do a game called Flying Circus which is one of the best WW1 sims out there.
For modern planes DCS World's base client is free and includes 1 plane, the SU25 ground attack aircraft. This is really fun to fly in itself but be warned all the DCS modules are designed to be as realistic a simulation as they can possible make on a PC. Almost all of the buttons and switches in the virtual cockpit can be interacted with in some way. There is also a sort of DCS lite called Flaming Cliffs, which tends more towards the game side of things, and is where most people are encouraged to start.
If you decide to get into it you will want a decent joystick at least and preferably a throttle as well.