Wouldn’t it be convenient to have a combined Greek NT and LXX? Well, last year the German Bible Society published one. You can buy it on Amazon here: LXX-NA28 Greek Bible (Biblia Graeca). It will cost you a pretty penny, though, over $100. See Abram K-J’s post with details here.
Of course, with smartphone technology you can get apps with LXX/NT, or just browse to a site like https://www.academic-bible.com/en/online-bibles/septuagint-lxx/read-the-bible-text/ where you can read the LXX or NT.
If you don’t need the critical apparatus and you don’t mind reading the traditional texts, you might want to check out the Zoe Brotherhood‘s Greek Bible, Continue reading