In order to install Opencart 4 you must have php 8.0+ installed
Also in the php.ini file you need to uncomment the following modules

extension=curl.so;
extension=gd.so;
extension=zip.so;

Note: If you don't have them on your system, install them. Replace the numbers 8.3 with your php version

apt-get install -y php8.3-curl php8.3-gd php8.3-zip

Restart PHP-FPM

systemctl restart php8.3-fpm

I want my site opencart4.com to be in a folder var/www/
Сreate a opencart4.com folder

mkdir /var/www/opencart4.com

Set folder permissions 755

chmod 755 /var/www/opencart4.com

Download Opencart 4

Unzip the archive and copy the contents of the upload folder to the opencart4.com folder
Rename config-dist.php to config.php and /admin/config-dist.php to /admin/config.php

Set folders and files permissions

Set permissions 777 for the cache directories

chmod 777 /var/www/opencart4.com/image/cache/
chmod 777 /var/www/opencart4.com/system/storage/cache/

And files config.php and /admin/config.php

chmod 777 /var/www/opencart4.com/config.php
chmod 777 /var/www/opencart4.com/admin/config.php

Now open our website in the browser

http://localhost/opencart4.com/

You must agree to the license agreement. Click Continue.

Pre-Installation page. Click Continue.
Opencart 4 Install NGINX

Configuration page
Opencart 4 Install NGINX
Click Continue.
Don't forget to delete your installation directory!

rm -r /var/www/opencart4.com/install

Now open the file default.conf

nano /etc/nginx/conf.d/default.conf

And write to it

server {
    listen		80;
    server_name	opencart4.com;

    root		/var/www/$server_name/;

    error_log	/var/log/nginx/opencart4.com.error.log;

    location / {
        try_files $uri $uri/ /index.php?q=$uri$args;
    }

    location ~ \.php$ {
        fastcgi_index index.php;
        fastcgi_pass unix:/run/php/php8.3-fpm.sock;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_split_path_info ^(.+?\.php)(/.*)$;
        try_files $uri =404;
        include fastcgi_params;
    }
}

Restart NGINX

service nginx restart

How to fully configure the NGINX server is described in this article