I’ve been blogging about 5-6 years now on a regular basis - just all sorts of tutorials on web development, frameworks, cs, devops, whatever I’m learning at the time. I’ve also written for a bunch of publications like DigitalOcean and make a lot of open source side projects, so there’s plenty of quality content. But it’s pretty much all JavaScript/Typescript/Node.
My biggest tip is to just always keep track of what you’re learning as you learn it. Learning Docker? Write down each command that successfully does what you want. Keep track of setbacks. By the time you learn it, you now have all the resources to make an extremely useful article for someone else.
Also, try to create something from start to finish - a working tutorial, and list all prerequisites. If you’re writing a tutorial, that is. That’s what I’m best at, I’m much worse at writing opinions.
Most of all, don’t be afraid to put anything out there.