Apple stops signing iOS 10.2.1, 10.3 following iOS 10.3.1 release
Apple on Monday stopped signing iOS 10.2.1 and iOS 10.3, effectively cutting off downgrades for iPhone, iPad, and iPod owners who have already made the leap to iOS 10.3.1.

Without signed code, iOS updates can't be installed. The tactic is a security and compatibility measure, but can create problems for people encountering newly-introduced bugs.
Released last month, iOS 10.3 switched devices to the more efficient Apple File System, and made some other additions such as a "Find My AirPods" feature and a reviews API.
iOS 10.3.1 was released on Apr. 3, and solved some problems with 10.3 including a Wi-Fi vulnerability. Apple also restored over-the-air updates for owners of the iPhone 5 and 5c, the last iPhones with 32-bit processors.
The next update, 10.3.2, is already in its second beta and appears to cut off support for 32-bit apps and hardware, meaning that 10.3.1 could be the last version of iOS for devices like the 5c.

Without signed code, iOS updates can't be installed. The tactic is a security and compatibility measure, but can create problems for people encountering newly-introduced bugs.
Released last month, iOS 10.3 switched devices to the more efficient Apple File System, and made some other additions such as a "Find My AirPods" feature and a reviews API.
iOS 10.3.1 was released on Apr. 3, and solved some problems with 10.3 including a Wi-Fi vulnerability. Apple also restored over-the-air updates for owners of the iPhone 5 and 5c, the last iPhones with 32-bit processors.
The next update, 10.3.2, is already in its second beta and appears to cut off support for 32-bit apps and hardware, meaning that 10.3.1 could be the last version of iOS for devices like the 5c.
Comments
I haven't seen anyone other than AppleInsider claim that 10.3.2 would be dropping support for 32-bit apps on 64-bit devices. That claim is illogical: Apple does not do that sort of large scale support cutoff in minor updates, only in major new versions.
The evidence is pointing to iOS 11 being the version that will drop support for 32-bit apps and devices. A 32-bit app cutoff at iOS 11 gives developers about six months to get their act together and update apps they and their users care enough about.
A 32-bit device cutoff at iOS 11 gives the iPhone 5 a maximum support window of about five years of being able to run the latest iOS version, which is the same as the iPhone 4s. (The iPad 4 gets one month less. The iPhone 5c gets one year less, due to being released a year later with an older processor, similar to the iPad mini's timing relative to the iPhone 4s.)
All apps, including built in ones like Settings, disappear from the homescreen; only things remaining are URLs saved to the homescreen, and any apps that continue to download and install from the queue of apps to be updated, after the corruption occurred.
Not clear what the cause is, but it keeps happening. Only "non standard" part of my setup is, that I have apps from several countries AppStores (e.g. public transit apps only available in local stores), and that for testing and comparison purposes, I have considerably more apps installed than the average user, but none of these are out of spec, even though they may not be very common.
Oddly this happens repeatedly on my devices, but nobody else seems to have the issue; if I'd be carrying sensitive information, with this pattern, I'd assume I was being hacked, but I don't know what anyone would want from me...