Darkness or Light? Philosophy in Knights of the Old Republic.

By the way, I read somewhere that Revan's plan with the Death Star failed because it stopped functioning... Maybe I read this about the second part... if so, I apologize for my ignorance, as I haven't played the second part yet :(. And what about Bastila? Or did they both become hermits together with Revan?

In the second part, as it should be, they prepared the development for the first part in advance... almost at the beginning, you can determine in simple dialogues what gender and which Side Revan was... and as a result, many dialogues were changed accordingly...
There are no mentions of the Star Forge or the Sith that Revan gathered... as if they never existed... I didn't hear the reason for the destruction of the army and the Star Forge in the dialogues... I didn't even hear that it existed for some time after the Civil War... About Bastila, only a few holographic recordings, again depending on the choice of side and gender of Revan... In any case, Revan left the Republic and went somewhere to fight a terrible enemy (as I wrote in the neighboring topic, most likely with the source of the Mandalorian invasion)... possibly to unknown regions of the galaxy, but there is a version that he went to a parallel galaxy to fight the threat of the Yuuzhan Vong (the expanded Star Wars universe and books)...
Depending on the choice of Revan's side, you can see Carth and Bastila a couple of times in scripted scenes...

Alex, I'm almost 100% sure that you always play as the dark side:D.

Specifically in the Star Wars universe, yes... Because here, evil is not presented as "evil" as in other universes - that is, in Star Wars, the Sith are not short-sighted, all-powerful, purely selfish, and sadistically cruel creatures, but are more like a variation of "Chaos" against "Order" from the Neverwinter Nights universe... The Sith are very life-loving and more human than the Jedi... they have many hidden virtues, abilities, and charm...
However, despite all this, in the dialogues of the second part, I made Revan a light side character... because seeing Bastila and having a little conversation with Carth is a pleasant moment...
But in Jedi Academy, I still chose the light side... because the development of the further plot in the skin of a Sith is too stupid... it's not very Star Wars-like...