For Android:
You can use DeployGate with any devices.
There is no limitation for the number of devices you want to distribute to. With our distribution page functionality, you can easily let your testers download and install your app from the distribution page URL.
For iOS:
If you will use for iOS devices, you can distribute your apps within the terms and conditions given by Apple’s Developer Program.
Regarding Apple Developer Program, you can distribute your apps up to 100 devices for both internal and external uses.
Apple Developer Enterprise Program, on the other hand, doesn’t have limits to registered devices but distribution is limited only to internal uses.