handlerURL returns 404 not found on apache2.4

[Peter Schober]

* JOHN G HEIM <jheim at math.wisc.edu> [2019-08-29 17:40]:
> alias /Shibboleth.sso /var/www/html

Glad you "fixed" it but the above is nonsensical: Clearly the
DirectoryIndex (or FallbackResource or directory content) of your
document root is not what should be served at the location
/Shibboleth.sso
So you're relying on a side-effect of that configuration.

Instead just look at the .htaccess file in Drupal's base directory
exposed to the web server (in your web servers DocumentRoot) and
exclude the SP's handler as explained by both Stephen and Scott.

Somewhere around here:
https://git.drupalcode.org/project/drupal/blob/8.8.x/.htaccess#L125

-peter