Scandinavian 3. d4


But I am still curious why 3. d4 suddenly has become popular this week. The games Yigor shows (thx!) are from 2019.

It’s probably just a coincidence. I think you should play Nc6, which forces Nf3, and then e5!? Is a good and strong option that I’ve had success otb with

Yeah it was in the book "The Modernized Nimzowitsch" by C Bauer. It is just as good as Bg4 with the added plus that black fights back immediately.

If you let Lc0 or SF15 run for a while, it has Nc3, Nf3, and d4 as the first 3 moves it recommends with a slight edge for White in all 3 variations. d4 will likely transpose into the Nf3 lines, but as it is the key break White wants to play in the opening, there is nothing wrong in playing it before developing the knight.
Black has 2 main ways to play: the long castle approach or the short castle approach. The former develops quickly, but runs with into White's activity (with the Be3/Be2/Nf3/d4/c4 setup, White is going to play on the queenside). The short castle approach is safer, but slower and has the problem of trying to find counterplay as White is given time to get his ideal setup.