[psiozos]

Pick one of the niches you are knowledgeable about, create an online course and go out and sell it.

An online course is a very versatile type of product, much easier to create than an ebook (or an app for that matter), much easier to promote, easier for people to consume, and much easier to monetize. Online courses are a booming trend. And you don't need any infrastucture to sell it, just a stripe account and a platform like https://www.learnworlds.com (disclosure, I am a co-founder there).

You would probably need a couple of hours to create some nice screencasts with the top linux commands. Make this a free course and share it across social media. Much easier than building an MVP app or site. If you see traction then double down and go for the paid "premium" course