I cannot set Safe Browser as the default browser for my Android 6.0 device

Symptoms
I have an Android 6.0 device. I am trying to set Safe Browser as the default browser for my device. However, I am not able to do this through the SAFE app.
Diagnosis
On most Android devices, you can set the default browser either through the SAFE app settings or through the device's system settings. However, on some Android devices, you are not able to set the default browser through the SAFE app - you must use the device's system settings.
Solution
If you cannot set Safe Browser as the default browser via the SAFE app, do it through system settings in the following way:
- Tap Settings > Apps > Configure apps.
- Under Advanced, tap Default Apps. The Default Apps page opens.
- Tap Browser app. The Browser app window opens.
- Tap F-Secure SAFE.
To set Safe Browser as the default browser through the SAFE app, do the following:
- Open your SAFE app.
- Tap Safe Browsing to open the Safe Browsing settings.
- Tap Set as default.
The Apps page of your device's system settings opens.
- Tap Configure apps.
- Under Advanced, tap Default Apps.
The Default Apps page opens.
- Tap Browser app.
The Browser app window opens.
- Tap F-Secure SAFE.
Safe Browser is now your default browser.