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.