Release Preview mobile build 14393.221 is live for Windows Insiders
The most stable Insider ring gets a new build for Mobile
Those on the Release Preview ring of the Windows Insider Program can upgrade their smartphones to Windows 10 Mobile Build 14393.221. This update comes without a changelog, but we assume it includes the usual minor fixes and performance improvements for the current branch.
If all goes well with this build, and assuming there is no better candidate in the foreseeable future, we can expect 14393.221 to be released for Production devices in the second week of October.
Microsoft has so far released 14393.221 only for Mobile devices, while the current PC build is 14393.187, available for both Insiders and non-Insiders.