You can 'share' the app using Testflight with a (large) group of known people. They must be invited by you to use it.
Testflight is primarily meant to enable beta testing, not to distribute live apps.
Here's your starting point: TestFlight Beta Testing - App Store - Apple Developer
You don't have to use XCode to get your app into Testflight. Upload of the .ipa per 'Application Loader' is possible as well, after preparing the upload with iTunesConnect.
If you just want to 'share' the app with Testflight, you don't need any special plugin.
Thanks VectorP! I discovered Application Loader and tried uploading my IPA. It failed App Store authorization for not having icons for iPhone5, iPod, etc. It's only built for iPad's though!
Is there a way to get to TestFlight without having to get App Store authorization?
Isn't there a Beta path?
There is no way around Apple's Developer account and Apple's review.
Now, what is it you really want to do? 'Share' the app is a bit vague.
Do you want to distribute your app without Apple knowing? Or do you have a small group of friends you want to have the app installed? Something else?
Corporate client not allowed to download iTunes so they can't install an IPA on their iPads for beta testing.
They CAN download TestFlight so I assume they could load the app without need iTunes.
Corporate client should be using an MDM solution (Mobile device management). This would let the corporate client distribute the IPA to whomever they chose without the need to go through Apple at all.
You might also try https://www.diawi.com/ , but I have no direct experience with them. You'd need a way to get the device IDs from users who are going to test your app.