There is not one single way to do deployments, and what you suggest leads people to vendor lock-ins, rather than the ability to self-host things on their own hardware later on (or if necessary). What I teach is actually a good approach for many, if not most people.
My intention wasn't writing a book on fancy-cloudy deploys for enterprises, but teaching people more about systems they use. I deploy my side projects the way I describe in the book, and I can tell you I have a good time, because everything is straightforward and easy-to-fix.
* Ad Server configuration: I explain deployment with and without containers. People can choose the right path for them. If you would read the book, you might have realized there is not all that much system configuration after all and it's easy to keep up.
* Ad Services with systemd: Hard disagree. systemd-based distributions (Fedora, CentOS, RHEL, Ubuntu, Debian) are eating the Linux world. systemd is an init system, so even if you don't write a systemd service on your own, you should understand how they work (your databases, firewalls, system services, and even Docker would be managed as a systemd service).
* Databases: This book is not an argument for running the database yourself, but about how you can do it with just 20 lines of Bash. People should decide themselves what's best for the project at hand.
* SELinux: You should absolutely learn it as it's a security layer of your Linux systems. Most resources skip it and then people don't feel confident running with SELinux, and thus deploy less secure systems.
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I see your whole argument looks like let's run Kubernetes. I don't think it's the right choice for indie hackers and early startups (the target audience of my book).
If you want to go the path of Kubernetes, than my book gives you a great introduction to networking and Docker which are prerequisites for understanding and working with K8s. And SSH, Puma configs, encrypted backups, and other topics are same whether you have K8s or not.
I only use Kubernetes at work, and I prefer doing things without it.