"App not installed"
The file is often incomplete, or a differently signed version is already installed. Download the APK again; if it persists, uninstall the old version and reinstall.
FAB-MIND-OSby Fabrice
Android guide
How to install an APK
Apps are APK files downloaded directly, without the Play Store. Here is how to install them in under a minute.
Step 1
Download the APK
Tap "Download" on the app page. The .apk file is saved to your phone's Downloads folder.
Step 2
Open the file
Tap the "Download complete" notification, or open the Files app › Downloads and tap the .apk file.
Step 3
Allow "Install unknown apps"
The first time, Android asks you to allow your browser (Chrome, Samsung Internet…) to install apps. Tap "Settings", turn on "Allow from this source", then go back. This is an Android security setting, needed only once per browser.
Step 4
Tap "Install"
Confirm the installation and wait a few seconds.
Step 5
Open the app
Tap "Open" or find the icon on your home screen. You're all set!
Troubleshooting
Play Protect warning
Play Protect may flag an app that doesn't come from the Play Store. Tap "More details" then "Install anyway" if you trust the publisher.
Not enough storage
Free up space (photos, videos, unused apps): installing needs about twice the APK size.
Updating an existing app
Download the new version and install it over the old one: your data is kept, no need to uninstall.