From your screenshot it looks like you’re getting an Apache 404, not a PrestaShop one.
URL: …/shop9/admin873…/login?_token=…
Apache is trying to open a real folder /admin873…/login and can’t find it, instead of passing the request to index.php in the admin folder.
In PS 9 the /login URL only works if URL rewriting is active in Apache and the .htaccess in the admin directory is being used.
1. Make sure mod_rewrite is enabled
sudo a2enmod rewrite
sudo systemctl restart apache2
2. In your Apache vhost for localhost the shop path must allow overrides, e.g.
<Directory /var/www/html> AllowOverride All </Directory>
3. Check that you have an .htaccess file in both /shop9/ and /shop9/admin873…/.
If the admin .htaccess is missing, copy it from a fresh PS9 install or re-generate it.
http://localhost/shop9/admin873…/index.php
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