How To Install Linux, Nginx, MariaDB, PHP (LEMP stack) on Debian 10_
https://www.digitalocean.com/community/questions/new?tags=LEMP%2CNginx%2CDebian+10

Above is OK.
Step 4 — Configuring Nginx to Use the PHP Processor
My_domain is “newpay191217.ml”

$ sudo mkdir /var/www/newpay191217.ml
$ sudo chown -R $USER:$USER /var/www/newpay191217.ml
$ sudo nano /etc/nginx/sites-available/newpay191217.ml

server {
    listen 80;
    listen [::]:80;

    root /var/www/newpay191217.ml;
    index index.php index.html index.htm;

    server_name newpay191217.ml www.newpay191217.ml;

    location / {
        try_files $uri $uri/ =404;
    }

    location ~ \.php$ {
        include snippets/fastcgi-php.conf;
        fastcgi_pass unix:/var/run/php/php7.3-fpm.sock;
    }
}

$ sudo ln -s /etc/nginx/sites-available/newpay191217.ml /etc/nginx/sites-enabled/
$ sudo nginx -t
$ sudo systemctl reload nginx

Step 5 — Creating a PHP File to Test Configuration, Show 404 Not Found

$ nano /var/www/your_domain/info.php

<?php
phpinfo();

http://www.newpay191217.ml

Welcome to nginx!
If you see this page, the nginx web server is successfully installed and working. Further configuration is required.
.....

http://www.newpay191217.ml/info.php

404 Not Found