Hi, here is some update:
Some Chinese mobile devices have spyware right in the system (“FOTAprofider” or “WirelessUpdate”). Avast detects it. More on https://android.gadgethacks.com/news/these-android-phones-could-be-affected-by-adups-chinese-spyware-0175014/
And as it is a part of the system, Avast Mobile Security has no chance to stop its installation or remove it. The only way to get rid of it is device software update; some mobile phone manufacturers have already released such spyware-removing updates.