If you install Magento 2.4 via Softaculous, you'll also have two-factor authentication enabled.
To get access to the admin interface, you'll have to disable the Two Factor Authentication module in Magento.
To do this, you have to access the console (e.g. Terminal in cPanel), go to the directory where your Magento installation is (Often public_html).
After this run:
php bin/magento module:disable Magento_TwoFactorAuth
You'll now be able to actually log into Magento.