Apparently updates are generally sent out to a few major networks EE, Vodafone etc. who test it and give feed back. Then any problems are sorted and sent back to EE etc. If EE etc are happy then EE and Vodafone will send it out as and update. Big companies can find bugs quickly. With smaller providers it can take ages and some may never get a copy. This clearly means that some networks will have different features abilities and stability which can be very upsetting for end users. Hence the dominance of Samsung and Apple to appear more stable across networks they can sort out issue more quickly.
Somewhere on this forum there is info that nearly 500,000 test have to be done just to get Google to allow the use of their apps on the Open Source Android.
Glad that’s not by job.
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So there is usually an alternative where you can download and install yourself.