With the latest release of Laravel 8 and laravel Nova 3.9, the minimum required PHP version is 7.4.9
On my mac I had php 7.4.7
To make this very small update, it's actually a bit more complicated that you might think.
With homebrew you want to execute these commands:
brew update
brew unlink [email protected]
brew install [email protected]
sudo rm -rf /usr/local/Cellar/php/7.4.*
And it should work if you run php -v