[kibwen]

By "immersive" are you thinking of first-person games like Doom? Sadly most first-person games prefer to use a mouse to control the camera, and most also reward twitch reflexes. You said you were willing to buy a joystick, so maybe you would enjoy a flight simulator? And if you wanted something more game-y, then the Mechwarrior franchise is a very immersive, slow, ponderous first-person game that makes good use of a joystick as well.

Sadly most games these days are not accustomed to be entirely controlled by a keyboard. However, any game that supports a controller should allow you to configure it to use a keyboard instead. The only games I can think of that are keyboard-first are old-school genres like MUDs and classic roguelikes. For a starter MUD I'd recommend DiscworldMUD, and for a starter roguelikes I'd recommend Dungeon Crawl Stone Soup (which is not quite "forgiving" in an absolute sense, but is relative to its genre). Both of these games are free, can be played in either the browser or a native MUD client/SSH terminal (respectively), are extremely Linux-friendly as a result, and are "immersive" in the sense that they invite you to use your imagination (although DCSS also has a graphical version).

If you're willing to be "immersed" by a game with a top-down perspective, I'll go out on a limb and recommend Moonring. It's free and made by a single indie developer and designed to evoke the classic Ultima-style RPGs of the 80s, but with modern conveniences and sensibilities. It gives you a free-form world to explore, and even if combat can sometimes be punishing you never really lose any progress for dying.

[bhattisatish]

DiscworldMUD has definitely piqued my interest. I own the whole pratchett's set. Something I can see myself enjoying :-)

Moonring seems interesting. A title I will definitely try.