You can use the default AppStream to upgrade PHP instead of using external repositories now.
# dnf module list php
To enable PHP version 7.4, simply use the command:
# dnf module enable php:7.4
You may encounter error of not possible to switch stream with an error like below:
If that is the case, then use the following command to reset:
# dnf module reset php
After the module is enabled to ver 7.4, you will need to switch to 7.4:
# dnf module switch-to php:7.4
After that, PHP is upgraded to ver 7.4
