How to change contents of Mariadb (MYSQL) Internal error, please check the log file error?

Question

MySQL

Can you please tell me whether it is possible to change the output of information in case of Mariadb service stop?
For experimentation and study, I stopped the mariadb service and when accessing the Wordpress site I get the error
Internal error, please check the log file, so I'm wondering where the output of this text is stored. Ideally, I need to display my HTML page.
NGINX webserver

error_page  500 503  /50x.html;
error_page  502 504  =500  /50x.html;
location = /50x.html {
    root /usr/share/nginx/html;
    internal;
}

I use this piece, PHP works for errors, but when the Mariadb service is stopped, a 500 error is given, the NGINX rule does not work for some reason, instead it says "internal error, please check the log file."