It’s easier to think about Linux on the context of what an individual application needs to run. Pretty much everything you do will have these components.
configuration
an executable
a communication mechanism (dbus, networking, web server, etc)
something that decides if the application runs or not (systemd, monit, docker/docker compose, kubernetes scheduler, or you as the user)
a way of accepting input (keyboard and mouse, web requests, database queries, etc)
a way of delivering an output (logging to unique log files, through syslog, or to stdout/stderr, showing something on a screen, playing a sound, returning a message to the client, etc)
storage (optional)
some cpu and memory capacity
That’s really it. If something isn’t working, it’s pretty much exclusively going to fall into one of those categories. What that means is going to vary significantly from app to app but understanding this is how literally everything works makes the troubleshooting process a lot easier.