Fresh Install -> 404 (/admin not found)

Hey there,
wanted to try grav and did a fresh install based on the grav-core+admin and some skeletons which all resulted in a 404 "The requested URL .../admin was not found on this server"; disregarding which of the .zips I tried. Neither the skeletons, nor the core .zips contained an /admin folder on the highest hierarchy, where some redirect seems to point.
Would be glad if someone could point out my error and help with the fix. Thanks!

A work-around till the problem is solved lies in the manual installation of the Admin plugin

Skeletons don't come with Admin preinstalled.

Grav+Admin on the other hand does, you maybe missed the .htaccess file? See the page not found doc