I ran into the same problem recently, and you're right that the Stealth plugin is no longer supported. However, because I finally realized that the Stealth plugin was the best option, I did a clean install of WordPress to the last version of WordPress that the Stealth plugin supported to figure out how the plugin works. Turns out, the only thing that the plugin is doing is creating a .htaccess file with some magic. The .htaccess file will look a little something like this:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^logout wp-login.php?action=logout&_wpnonce=asdfasdf&stealth_out_key=asdfasdfasdfasdf [L]
RewriteRule ^login wp-login.php?stealth_in_key=asdfasdfasdf&redirect_to=http://example.com/login [R,L]
RewriteRule ^admin wp-admin/?stealth_admin_key=asdfasdfasdfasdf [R,L]
RewriteCond %{HTTP_REFERER} !^http://example.com/wp-admin
RewriteCond %{HTTP_REFERER} !^http://example.com/wp-login\.php
RewriteCond %{HTTP_REFERER} !^http://example.com/login
RewriteCond %{HTTP_REFERER} !^http://example.com/admin
RewriteCond %{QUERY_STRING} !^stealth_in_key=asdfasdfasdfasdf
RewriteCond %{QUERY_STRING} !^stealth_out_key=asdfasdfasdfasdfasd
RewriteCond %{QUERY_STRING} !^stealth_reg_key=asdfasdfasdfasdfasdf
RewriteCond %{QUERY_STRING} !^stealth_admin_key=asdfasdfasdfasdfasdf
RewriteRule ^wp-login\.php http://example.com [R,L]
RewriteCond %{QUERY_STRING} ^loggedout=true
RewriteRule ^wp-login\.php http://example.com [R,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
I have changed all of the keys to some variation of "asdfasdfasdf" -- obviously you would need to create some secret keys for yourself.
Hope this helps!