I admit I'm not smart enough... got curious about Mario Kart Tour ending service... so I downloaded an .apk and extracted it.
I've found some interesting stuff:
1- Contains .zst files, protected by encryption.
2- Contains data.unity3d files.
3- As far as I understood from an already existing preservation attempt (More info:
Click)
- MarioKart.apk is a host, and it uses Cache + DeviceID (or Nintendo Account ID) + Nintendo Server. If those three matches, it downloads assets from Nintendo Servers.
- If we had Cache data from every tour + decryption keys (which I already might or might not have

) + custom server, we could totally create an offline version of Mario Kart Tour.
Pure guess on my side, btw.