Another reason to write your own technical content, even if a similar question/answer does exist on SO, especially in examples where you experiment to put together examples that show/prove a point, is that it is practise for yourself.
I intend to get some of my own content out there (it may never happen, the intention has existed for quite some time!) and if I ever find time to do it some of the things I might include are expansions of things I've given as SO answers, expanding on details that might have been too much in the SO/SE context and potentially caused confusion or sliding off into tangents that would be too far off-topic from the starting point. I might not ever point people at this writing, the main point of it will be my own practise (of technical matters, and just the act or writing and organising information). If it comes to be something that feels useful then it might be the start of an online portfolio that I selectively send people to, or feed back into SO/SE (i.e. giving an answer with bits extracted from something I've already written with a “for some related tangents you might find this fuller article useful” link, as I already do for other people's articles like the very useful tomes of MS SQL knowledge at https://www.sommarskog.se/ that I've referenced on DBA.SE before now).
I write technical stuff to convince myself that I understand a topic. I'll write a tutorial for myself on it, and during this, ask questions that someone who doesn't know it at all would ask, sometimes I don't know the answer so I need to research more.
But at the end I can end up with a pretty good, in-depth, tutorial / notes / blog post.
I just don't publish them to the internet. But I find it's a pretty good way of checking how well you understand something. Like rubber duck debugging with yourself in a way.
There was a thread somewhat related to this recently. I’m wary of having anything that’s not direct professional experience directly listed in the resume.
The consensus is just that outside rare occasion or notability in your field, no one cares about your blog/project/GH/etc.
If I mentioned it directly on a CV at all I would list it in the very small personal interests section at the end along with my other hobbies (running, HEMA, etc.). I've not needed to update my CV in a long time, so advice on this may have changed, but way back when I last touched it up it was worth including such a short list of “what I do in my spare time” and interviewers would sometimes pick something off that as a starting point for a bit of informal discussion.
Though of course it will be linked from my main “vanity page” (which also doesn't currently exist in any touched-in-the-last-decade form) at forename.surname.net or similar, which would be listed on my CV along with other contact details, as well as being linked to on other relevant online profiles. An interested employer might look, those that don't care won't be affected either way.
I intend to get some of my own content out there (it may never happen, the intention has existed for quite some time!) and if I ever find time to do it some of the things I might include are expansions of things I've given as SO answers, expanding on details that might have been too much in the SO/SE context and potentially caused confusion or sliding off into tangents that would be too far off-topic from the starting point. I might not ever point people at this writing, the main point of it will be my own practise (of technical matters, and just the act or writing and organising information). If it comes to be something that feels useful then it might be the start of an online portfolio that I selectively send people to, or feed back into SO/SE (i.e. giving an answer with bits extracted from something I've already written with a “for some related tangents you might find this fuller article useful” link, as I already do for other people's articles like the very useful tomes of MS SQL knowledge at https://www.sommarskog.se/ that I've referenced on DBA.SE before now).