I have the same error and I enabled the debug on the wp-config file to find this.
Fatal error: Uncaught Error: Call to undefined function mysql_connect() in C:\Apache24\htdocs\clickmedia\wp-includes\wp-db.php:1658 Stack trace: #0 C:\Apache24\htdocs\clickmedia\wp-includes\wp-db.php(631): wpdb->db_connect() #1 C:\Apache24\htdocs\clickmedia\wp-includes\load.php(426): wpdb->__construct(‘admin’, ‘081447Addax’, ‘clickmedia’, ‘127.0.0.1’) #2 C:\Apache24\htdocs\clickmedia\wp-settings.php(126): require_wp_db() #3 C:\Apache24\htdocs\clickmedia\wp-config.php(90): require_once(‘C:\\Apache24\\htd…’) #4 C:\Apache24\htdocs\clickmedia\wp-load.php(37): require_once(‘C:\\Apache24\\htd…’) #5 C:\Apache24\htdocs\clickmedia\wp-blog-header.php(13): require_once(‘C:\\Apache24\\htd…’) #6 C:\Apache24\htdocs\clickmedia\index.php(17): require(‘C:\\Apache24\\htd…’) #7 {main} thrown in C:\Apache24\htdocs\clickmedia\wp-includes\wp-db.php on line 1658
I have also looked for the nd_mysql but I don’t have it on my extension list on the php.ini
These are the extensions that are currently enabled
C:\Users\User>php -m
[PHP Modules]
bcmath
calendar
Core
ctype
date
dom
filter
hash
iconv
json
libxml
mysqli
mysqlnd
pcre
PDO
Phar
readline
Reflection
session
SimpleXML
SPL
standard
tokenizer
xml
xmlreader
xmlwriter
zip
zlib
I am also running on a local machine, PHP 7.4.5
I also don’t have the PHP configuration application to enable or disable as one suggested. So I use the PHP.ini file to make changes.