Why does core update result in 'The requested page could not be found'?
i found nginx drupal 8 host config here https://www.nginx.com/resources/wiki/start/topics/recipes/drupal/

my config is this

server {
server_name www.EXAMPLE.COM .EXAMPLE.COM;
root /var/www/EXAMPLE.COM/www;

location = /favicon.ico {
    log_not_found off;
    access_log off;
}

location = /robots.txt {
    allow all;
    log_not_found off;
    access_log off;
}

# Very rarely should these ever be accessed outside of your lan
location ~* \.(txt|log)$ {
    allow 192.168.0.0/16;
    deny all;
}

location ~ \..*/.*\.php$ {
    return 403;
}

location ~ ^/sites/.*/private/ {
    return 403;
}

# Block access to "hidden" files and directories whose names begin with a
# period. This includes directories used by version control systems such
# as Subversion or Git to store control files.
location ~ (^|/)\. {
    return 403;
}

location / {
    # try_files $uri @rewrite; # For Drupal &lt;= 6
    try_files $uri /index.php?$query_string; # For Drupal &gt;= 7
}

location @rewrite {
    rewrite ^/(.*)$ /index.php?q=$1;
}

location ~ '\.php$|^/update.php' {
    fastcgi_split_path_info ^(.+?\.php)(|/.*)$;
    #NOTE: You should have "cgi.fix_pathinfo = 0;" in php.ini

    include             /etc/nginx/conf.d/fastcgi_params.conf;

    fastcgi_param       SCRIPT_FILENAME     /var/www/EXAMPLE.COM/www$fastcgi_script_name;
    fastcgi_param       DOCUMENT_ROOT       /var/www/EXAMPLE.COM/www;

    fastcgi_param       PHP_ADMIN_VALUE     upload_tmp_dir=/var/www/EXAMPLE.COM/tmp/upload;
    fastcgi_param       PHP_ADMIN_VALUE     session.save_path=/var/www/EXAMPLE.COM/tmp/sessions;
}

# Fighting with Styles? This little gem is amazing.
# location ~ ^/sites/.*/files/imagecache/ { # For Drupal &lt;= 6
location ~ ^/sites/.*/files/styles/ { # For Drpal &gt;= 7
    try_files $uri @rewrite;
}

location ~* \.(js|css|png|jpg|jpeg|gif|ico)$ {
    expires max;
    log_not_found off;
}
}


AND the problem disappears.