I have now seen: Season 1 and 2, Ilse's Notebook, No Regrets and Lost Girls. Is there ANYTHING I can watch from Attack on Titan? I only watch season 3 when it comes out in German, so that doesn't apply! ^^
The manga.
You can read manga (in German) up to volume 29 in the middle of season 4.
Nothing more besides manga?
If you want dub just have to wait a few years…
There's also the manga series Attack on Titan before the Fall. Will probably never get an anime adaptation.