Mac OSX Catalina: can’t be opened because Apple cannot check for malicious software

Mac OSX Catalina: can’t be opened because Apple cannot check for malicious software
macOS cannot verify that this app is free from malware.

Solution:

• check with Security&Privacy settings under System Preferences to lift the Gatekeeper blocks, and fix alert messages.
• when you are using Catalina, the warning message reappears every time you open the non-notarized app
• open Terminal and run the cmd below

xattr -d com.apple.quarantine /Applications/<your App's Name>.app

e.g.: 
xattr -d com.apple.quarantine /Applications/qbittorrent.app