"Android isn't Linux," of course. This is a very obviously false myth that is debunked very easily by simply looking at any Android device or the source code. It is not a myth spread by people who are technologically literate. Yet, this easily verifiable fact upsets Linux fans so much they resort to downvotes and ugly language (I have my ideas why, but it's probably a waste of time to elaborate in this thread).

Of course, the more savvy among the Linux fandom will admit that Android "contains Linux, but isn't real Linux" - but "real Linux" is yet another myth; that is, the myth that there is more to Linux than an operating system kernel, a myth that leads to further myths such as the myth of fragmentation, or the myth that distributions are worthless and we need a "unified app store." It's a myth that clouds history and assigns the wrong motives to the wrong people and meanings to things that don't need or deserve them (the misunderstanding that that "Linux" is "about openness" or "against corporations" for example, when large companies are the main contributors to and users of the Linux project). Linus Torvalds himself says he only cares about code, not about freedom or openness or any of that stuff (that's Richard Stallman's thing)

The fact that this myth is widely believed is not relevant. We don't live in a world where a falsehood becomes true if it is widely believed; people used to believe the sun revolved around the earth, for example. Also, a falsehood being widely believed doesn't mean it deserves to stay unchallenged.

The point of reminding Linux fans that Android is based on their beloved kernel isn't meant to be a well-actually or anything. It's a reminder that much of what a so called "Linux phone" can do is already possible without having to switch to an operating system that in many respects is not ready for general use. For example, you can run xfce in Termux - I hope this is enough to disabuse one of the silly notion of "not real Linux." For some reason. people looking for so-called "Linux phones" desire Android compatibility, and it turns out that because Android itself is Linux, it is far easier for Android to run so-called "Linux apps" than it is for so-called "mobile Linux" to run Android apps.

Android is Linux and that's a good thing. I should point out that it's not my preferred Linux operating system - I was a Pinephone early adopter and used to daily drive Mobian, I would prefer that or GNU Guix over Android. Still, not only is it a Linux based operating system, it also has its own rich free software ecosystem backed by F-Droid. It's very usable once you cut out the Google crap and stick to free software only (or as much as possible).

I wrote more on the "real Linux" myth here in case anyone's interested in more reading material.