Kenobi, definitely. The story and plot follow him, not either of the others. He's protecting Leia, but the focus is on him, not her. Sort of like how Grogu can't be argued to be the main character of the Mandalorian.

Reva is the big one, I think a lot of people are going to argue her simply because they dislike her, so they think she's overused. She's the main antagonist at the beginning, she gets much less focus then Obi-Wan. Probably like 20 minutes of screen time in the first two episodes, from what I remember. Kenobi has like 50

Kenobi and Leia got more screen time, but Reva seemed to get more character development.

I would say Obi-Wan Kenobi because he is the main focus of the show and the story follows him and his journey

Also it's called Obi-Wan Kenobi for a reason

Technically you never specified that this was Kenobi, so I can't say. Also, I haven't watched it.

Obi-Wan. I can't fathom why people think that Reva is the real main character when her relevance ended before the show even did.