All rumors but possibly HUGE spoilers for Obi-Wan, so it's black ghost text for the lot of it. This isn't everything, just some points I think are interesting. These are all from makingstarwars.net.
The first Obi-Wan episode opens up with a scene at the Jedi temple during Order 66 where two older Jedi Masters die protecting 1-2 teenage Padawans, who manage to escape. Grogu is not in these scenes, but a de-aged Anakin might be.
One of the Padawans somehow figures out that Obi-Wan went to Tatooine and comes looking for him. The Padawan doesn't know anything about Luke or Leia of course, so he/she thinks they can find Obi-Wan, restart the Order together, etc.
Not one, not two, but three Inquisitors follow the Padawan to Tatooine - a Grand Inquisitor - not sure if it's the same character from Rebels, the Third Sister, whose name is Reva and is played by actress Moses Ingram from the Queen's Gambit, and the Fifth Brother.
The Grand Inquisitor was voiced by Jason Isaacs in Rebels and this version will be played by Rupert Friend,
The Fifth Brother was in Rebels as well, grey skin, wore a hat, got killed by Maul on Malachor.
The Third Sister thinks she senses Obi-Wan on Tatooine but the Grand Inquisitor tells her she's an idiot.
Each of the 6 episodes is around 45 minutes long, so it's the equivalent of a 4 hour, 30 minute movie.
Princess Leia is kidnapped specifically as a plot by the Inquisitors to lure Obi-Wan out to kill him because they know of his association with Bail Organa. Apparently there is stuff on Alderaan with Leia in a young diplomat program. Vivien Lyra Blair from Bird Box is young Leia.
Supposedly a few scenes showing what Luke's life is like (sucks) vs. what Leia's life is like (awesome) growing up.
The Lars' family is in Mos Eisley shopping and selling water and sees Inquisitors harshly interrogating people about Jedi. Later Owen meets Obi-Wan in the desert and berates him for attracting danger to Tatooine - even though it's the other Jedi who did so.
The Jedi Padawan finds Obi-Wan who repeatedly denies that is who he is - saying his name is Ben. The Padawan recognizes him from the Temple but Obi-Wan won't admit to it because he thinks it will jeopardize Luke's safety. He tells the Padawan that the war is lost and he should bury his lightsaber in the desert if he wants to survive. The Padawan eventually leaves.
When Obi-Wan gets the call from Bail that Leia is in trouble he goes to the spaceport and finds sees that the Inquisitors have killed the Padawan and strung his body up, I imagine like in Game of Thrones, as a warning.
