Ok, I finally got it.
I'll write it here for anyone with the same problem, or for future reference.
First, check that you have BusyBox installed.
Then, in Magisk Manager, install the Audio Modification Library. Reboot.
In Magisk Manager again, ins...
Hi, how did you get Viper installed please? When I download magisk module it's always asks for driver install. Even if it's once installed.
I had trouble too.
Try with the instructions in the last message on this thread: