/var/www/vhosts/example.com/app/views <- this path is linked to the path above
The Issue
if i try to use a view from a sub directory in /views for example /views/admin i got a 500er error and a "Error - The requested view could not be found: /admin/dashboard.html.twig"
Northing wrong with that, we use symlinks to make theme files public.
It is most likely that your webserver doesn't have the permission to read the files, you need to give specific config to allow symlinks to be followed (it is a security measure), and if you're on Redhat, it might also be selinux that is blocking access...
What OS? What webserver? Did you check if follow symlinks is enabled? Did you check if there is no SELinux or AppArmor blocking access?
Did you create the test.php to check what the exact error is that you get when you try to read the file? Did you check what the webserver and/or PHP log file says?