I'm pretty sure it's written with the conceit that it's a historical document, rather than in the style of a traditional novel, so the granularity isn't at a level that necessarily includes secret love affairs, and even some elements that are included could theoretically be character assassination in universe by a biased historian.

Like one character in the book is noted to have died after falling off her horse, and in the show she is murdered on screen by another character.

I believe they've also changed some things (folding two characters into one, making characters more or less influential, etc), which, to be clear, isn't a value judgement, I think that is often a good idea for an adaptation.

The showrunners aren't following the book very closely at all. They're just kinda adding their own plotlines, character relationships, characterization, etc, and using "well the book is an unreliable history" as an excuse as if the book didn't give three competing narratives and enough information for a reader to figure out what's probably true and what's definitely not. They've taken it from "here's an unreliable history, puzzle it out" to "this history is unreliable, so let's just write whatever we want."

Also in the final episode

Haven't watched the show but the book was pretty good and the show ruined some of the most impactful scenes.

The story is that the Stormtroopers as an organization grew out of the Clone Troopers, but started recruiting normal humans after the Order 66. Not that it really matters.

The Rohirrim speak the irl mercian dialect of Old English. Tolkien was for sure going for Germanic which is close enough. My Black Elf issue in rings of power isn't that everyone isn't white, it's and this is mostly the proto Hobbits and men, elves can be pretty reasonably explained, that it's done kinda at random. Like in an entire town of white dudes there's 3 black charscrers. Where are the other black people then? Do these people have family? Are they from somewhere else either recently or ancestral? Big part of Tolkien non LOTR middle earth stuff has a great deal to do with the movements and mixings of different cultures over a vast span of years and by the second age thousands of years of migrations and cultural exchange has happened and could be reflected in the diversity of the casting. It could be made to blend very well with tolkien's world building. It reflects more on the show being super lazy in that regard pretty much across the board more than anything.

The two gay ships people are having a meltdown over don't happen in the book. In one case the relationship between the two characters is very different and both ships likely wouldn't be depicted whether they occurred because the book is written as a history text book, with a biased author pulling from biased sources.

The book is based on is a historical book written years after the events, with contradictory relates. For the war the show is adapting, the main sources are a maester and the queen's buffoon. Also, this second season were something like 20 pages of the book, where only 3 relevant things are mentioned, blood and cheese, the dragon fight in rook nest and the dragon seeds. Basically everything else is made up by the showrunners.