I saw this Chinese company offering a demo for their app/service which is a .ipa
file. You can simply visit a link by your iPhone via Safari and you can install
Xcode 9 gives over-the-air installation build option for adhoc distribution.
But apple seems not providing a basic installation html page. So, one needs to create one as shown here.
Here goes the html of such a page from that site.
Install Geoloqi
Congrats! You've been invited to the beta of Geoloqi.