Organize the following methods for you, and allow the installation of software from unknown sources on your mobile phone:

1, ColorOS 12 and above: "Settings > Passwords and Security > System Security > External Source Applications".

2. Coloros11.0-1.3 version: "Settings > Security > Install External Source Applications".

3. version 7.0-7.2 of coloros: "settings > other settings > devices and privacy > install external source applications" turns on the corresponding application switch to install the software downloaded from the application.

This answer is applicable to all OPPO models of ColorOS 7.0 and above.