I get puzzled by people who faithfully watch successive episodes of a series that they then claim to be utterly dull and to have spoiled the book. Why are they still watching?
Myself, I was not surprised that a lot changed. The original stories often have nothing but people talking. That would get a limited audience.
It is also fun to be surprised by interesting plot changes. And as the ending of the last episode suggested, we catch up with Gaal's future, as well as seeing some of her past. Very nicely done. She is both vulnerable and extremely clever. And I'm certainly not someone who's bothered by a young dark-skinned woman showing those qualities.
I'd been assuming all along that she is somehow tied to the Second Foundation. Which Seldon has never mentioned, unlike the book, but actually this is more sensible. A broad hint about a deep secret is decidedly odd.
But a lot happens back at Terminus. From Episode 4, I guessed that the elegant Lord Dorwin, Chancellor of the Empire, was not going to appear. In fact he has been changed into a mere warship captain. I still think it sad they didn't include this fascinating character in some guise or other.
At the end of episode 4, the state of play at Terminus looks impossible. Now we have to wonder what happens next. But given assurances that the mysterious mind-influencing object found on arrival is not the book's vault showing recordings of Harry Seldon, I speculate that it is for mass mind control.