I recently found a mobile game with very good graphic. It use unity ( as I can load only some basic geometry in assetstudio from the base apk) . Anyway all the content is stored in .pak files with this header

If someone want to take a look here some sample : https://mega.nz/file/4p4jHKyR#dsiC_gGel ... EBSMpbyUjU
Here you could download the apk (1 gb) : https://apkcombo.com/九天訣-馬上來戰/com.indie.zll2.google.ft/
EDIT :
other sample, first bytes of the 2 main .pak files : https://www.mediafire.com/file/sloylp1n ... 2.rar/file