Force Apache directory listing even if DirectoryIndex files are present
Solution 1:
You may leave DirectoryIndex option empty or just turn off dir_module module.
Solution 2:
The DirectoryIndex directive can be limited in scope with a Directory block
<Directory /path/to/directory/to/list>
Options +Indexes +MultiViews
DirectoryIndex will-never-exist.xyz
</Directory>
This limits the scope to the particular directory rather than your vhost or server etc.