Since Mac OS 10.11, Apple has increased security features with System Integrity Protection (SIP), so some software that has high access to the error system cannot be installed. Especially on macOS Catalina, turning off gatekeeper is not enough. You need to disable SIP to be able to run applications outside of the App Store.
To turn off SIP, follow these instructions:
1. Reboot the device, hold Command + R to enter recovery mode while booting.
2. Select Terminal.
Type the following command to turn off SIP completely.
3. Type reboot to restart the computer.
The device has been turned off SIP mode, app was installed with less error-prone, especially on Catalina 10.15 version. If you want to install applications outside the App Store, you must turn off SIP.
Re-enable SIP function:
In case you need to re-enable the SIP feature, repeat the above steps. Type the following command in terminal:
Then reboot to use, have fun!!!