Tyla who was apparently accidentally revealed for Sziget was now announced for Open’er. Makes it even more likely she was pushed to next announcement maybe due ti Open’er’s deal with Tyla.
Metro 10 gets you to the nearest metro station. There is then a tram which goes 1 or 2 short stops getting you near the festival entrance.
Aside from buses, this is the best connection from the centre to the site and, as it is a hike, I'd recommend staying somewhere along that metro line.
I found it a bit of a mess last year (think my thoughts are in the 2024 thread) and that was even staying close to the festival.