It should start with how to make your system upgradeable too. I've server that started on Ubuntu 16 and made a helluva mess upgrading to 18. Due to php changes i've had to use ondrej's packages for later php... but that will break on a (very overdue) upgrade to 20...

All these script kiddie tutorials are terrible at showing how to maintain a server for years.

This is where docker really shines. Unless you’re a php developer or have a lot of experience with it, gluing it all together is best left to some clever person maintaining an upstream docker image.

Docker is not a good solution. Many security focused systems (important for self-hosting) are on FreeBSD. FreeBSD doesn't allow docker, because of it's major security vulnerabilities.

Docker is great for getting toy projects to work somewhere as a last resort, if the dependencies are strange and you need a convoluted (read: badly thrown together) environment to set up the app.

A well made application should not need docker to run.

What do you mean? The world is running on containers.

Docker and I are not friends. The quickest way I found to fill up my limited VPS hard drive was to install Docker. All the work arounds to limit it failed. Then there's the whole lack of concrete control over iptables, where a tiny mistake can open you up to all sorts of horrors. So, it's great that Docker works for many, but I get the exact opposite of warm and fuzzy for it however.

Perhaps Nix could help? It's great for configuration and reproducible builds without the overhead of containers (which in practice aren't often reproducible).

I think the hard part is that would be largely dependent on specific implementation, which itself is very opinionated. I could write a post on how I run, maintain, and secure Docker Container X on Ubuntu Y using vSphere with Synology and get 100 comments on why CentOS is better and I'm wasting time/money with vSphere over Proxmox, etc. Cloud doesn't have quite this problem. Once you've chosen a cloud provider, you have significantly fewer options in each category, minimizing this option-overload.

Write your howto on your private blog and disable comments. Problem solved. You can thank me later :-)

These are called instruction manuals and no one likes to read them.

I realy hate the part when they say "But this is outside of the scope of this manual."

I am certain you have spent the time to ask everyone if they indeed do not like to read these, but I disagree.