Greetings in that Divine and Most Precious Name of Our Lord and Savior Jesus Christ!T
I have a copy of the tanak in Hebrew in my house and it clearly says YHWH in Hebrew
(a) The Tanakh is a modern translation
(b) the oldest Hebrew manuscripts are medieval which is why the Church uses the Septuagint
h stands for T
orah (Law), N
evi'im (Prophets) & K
etivum (Writings). It is not a modern translation, it is not a translation at all in fact, unless you mean the Tanakh in modern Israeli Hebrew which is not the same as that of the Masoretic text or any previous Hebrew text.
The Tetragrammaton (YHWH) is found in pre Masoretic Hebew texts such as the Dead Sea Scrolls which pre date Christ, so it is not true that the oldest Hebrew MSS are medieval.
There are also Greek DSS, again which pre date Christ, which contain the Tetragrammaton in Paleo Hebrew script. So the Tetragrammaton did not suddenly appear out of nowhere in the middle ages.
It is also in the Samaritan Pentateuch, which also predates the Masoretic text. Both the Peshitta Old Testament and Targums, which pre date the Masoretic text, contain a more obvious marker for the Tetragrammaton than LORD, Peshitta - MarYah (Lord Yah), Targums - Yah.
And finally Jesus' own name contains the Divine Name, Yeshua literally means "Yahweh saves". The Divine name is contained in many other Hebrew names as well such as Eliyahu (Elijah) which literally means "Yahweh is my God".