I thought in an interview somewhere, the showrunners said they were pulling elements from across the entire Foundation cycle. It is remixed into a somewhat different narrative structure - probably to make it much easier and more linear to film. Though there is also the advantage of being able to plan for retcons and additions that happened over the course of the series.
Without giving spoilers, Asimov re-thought aspects of the setting towards the end. He merged in additional elements that were not originally conceived as part of the worldbuilding. I believe the first season of the show already incorporates some of these additions from the start.
Some of the negative reviews have already criticized the first season for being a vague adaptation - only "inspired by" rather than what the critic feels is an actual attempt to adapt the text. The thing is though, Foundation is a somewhat awkward collection of texts - a series of shorts and novellas; stand-alone books, sequels, re-packagings with new chapters, and prequel books.
I'm not sure how you could adapt it to any medium without viewing it as a collection of characters, story arcs, and ideas to be reorganized into something that will inevitably be similar yet very different.