I have a question concerning the three texts of Torah. I searched in the internet to know the 6000 differences between the three, and found that supposedly 1900 of them where the Septuagint agrees with the Samaritan [editor’s note: the questioner is referring here to the Samaritan Pentateuch], but I found nothing. Do you know a webpage or a book on the internet where I can found these differences?
You can find lists of differences between the Samaritan Pentateuch and the Masoretic Texts because both are in Hebrew, but to enumerate differences between the Septuagint and the Masoretic is difficult if not impossible, simply because the Septuagint is in Greek and the Masoretic is in Hebrew. Technically, they cannot “differ” because one is a translation. If you had a word in an English translation and a word in an Egyptian translation, how could you know if one reflected a different original Greek source? This might be difficult. Of course, some textual differences can be detected, despite the language difference, as certain Hebrew words in the Masoretic would be at such odds with the Septuagint and certain Greek words in the Septuagint would be at such odds with the Hebrew Masoretic that a scholar could declare clearly there is a “difference.” You can occasionally detect this in the margin notes of your Bibles as it may say in the margin things like “Septuagint: xxxxx” or “Masoretic: xxxxx” or “Dead Sea Scrolls: xxxxx”. Another point is that in the DSS, there are some Hebrew texts which are more similar to the Septuagint than to the Masoretic. This also can help to find “differences” between the Septuagint and the Masoretic, but, again, to enumerate is difficult.
So, I believe your request for a site that enumerates or lists all differences between the Masoretic and the Septuagint will not be met. What you can do, and what will be more helpful anyway, is when you are studying a particular passage in the Old Testament, look at the Masoretic, the DSS and the Septuagint and take every case one at a time. For example, you could look at the Masoretic, the Dead Sea Scroll and the Septuagint translation of Isaiah 7:14. This is the famous one about the virgin being with child. You can compare the three and decide for yourself what the original was, as well as its likely meaning, given the Septuagint translation.
I found a useful and readable article on the differences here: https://blogs.ancientfaith.com/departinghoreb/masoretic-hebrew-vs-septuagint-part-1/
Bear in mind, however, that this article makes it appear as if the differences between the text types is greater than it actually is. The vast majority of these 6000 differences involve very minor differences of spelling and word order.
Here is another article: http://www.septuagint.net/septuagint.htm
Sorry for a somewhat unsatisfactory answer.