/etc/nginx/sites-available/default

location /phpmyadmin {
    root /usr/share/;
    index index.php index.html index.htm;
    location ~ ^/phpmyadmin/(.+\.php)$ {
        try_files $uri =404;
        root /usr/share/;
        fastcgi_pass unix:/run/php/php7.2-fpm.sock;
        fastcgi_index index.php;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        include /etc/nginx/fastcgi_params;
    }

    location ~* ^/phpmyadmin/(.+\.(jpg|jpeg|gif|css|png|js|ico|html|xml|txt))$ {
        root /usr/share/;
    }
}