WieWaldi I got this book: Sight-Reading & Harmony (Complete Edition)
It contains about 160 one-liners in different keys (from 3 flats over plain C up to 3 sharps). Each one-liner is printed in 5 different difficulty levels on one page. All the one-liners are chorales - with a German title (no lyrics, haha).
I tried to do it, but I gave up when I was confronted with keys I couldn't play. I said to myself: If I get to a piece with a new key, I practice the scale in this key, before. And then things got boring
In the publicity for the book you mentioned, I see this: "The four-part chorales of J.S. Bach are regarded by most educators as the “ultimate litmus test” in music reading and sight-reading." I don't agree. If you spend a lot of time playing through chorales, you're going to get very good at - - - playing chorales. That's fine if you adore chorales, they never bore you and you don't want to play anything else. But if you want to get good at reading other styles, you need to practice reading those styles.
I also looked at the sample page. Each example is only half a chorale! No wonder you got bored. It's as if you were given a book of 4-line poems, but each one was cut off after the second line, so you never got to the end of a poem.
If you want to get better at sight-reading without boring yourself to death, you need to read complete pieces. Pieces that tell stories. All sorts of stories: short ones, long ones, sad ones, happy ones...
You already posted a list of compilations. There are some good ideas there: I'd have a look at the Classics to Moderns series. Apart from that, just look for piano music anywhere you can find it: in secondhand shops, in libraries, on the internet... Discovering stuff yourself is fun!
If a piece doesn't look ridiculously hard to you, put it on the piano and try to play the first few bars. Just the first phrase. Can you see where that phrase ends? Even if you play it very slowly, even if you make mistakes, can you work out how it ought to sound? If you thinks you've sussed out that phrase, great: it doesn't matter for the moment if you can't play it up to speed. Go on to the next phrase, do the same thing and slowly you will see and hear the story of the piece unfold.