Distributions based on Linux tend to provide there own curated repositories (any of the well managed major distros anyhow). The distributions are the product; multiple distributions compete just like any product category with more than one product brand.
Ship your software with an open source license and the distributions will do the work to include it; you target one standard build.
Ship your software with a closed source license but target the major parent distributions; get it into the Debian non-free repository and all those distributions based on Debian will inherit your software also. You target the major distribution build and you also get Ubuntu, Mint and the rest of the forks.
Build for Debian and Red Hat allowing child fork distributions to inherit the software and your covered. Easy-Peasy.
Basically the "oh nos, there's all these different products based on this one kernel and we have to target them all individually" argument is crap. Fragmentation would be several separate distributions claiming to be the same brand name and claiming to function out of the same repositories.
Which is actually what we do have with Android; multiple customized OS distributions with vendor specific changes and limitations all claiming to be the original parent Google Android version. If it doesn't have Google's standard interface and doesn't get it's updates directly and promptly from Google's repository then it's not Google Android.. it's a child fork OS distribution which happens to be based on it.
Amazon at least does it right. When they forked Android to make there own embedded OS, they said "this is our product and it uses our software repository".. and you get updates from amazon (not sure how promptly but at least you get updates). They don't say "this is Android.. on some device or another.. buy it", they instead says "this is Kindle Fire.. our device that does these neat things."
For me, the distribution is the product regardless of what OS kernel it may or may not use. And, if it's not a Nexus device with Google's stock os and direct updates then it's not Android.. some other distribution based on Android.
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