I could go in-depth, but really, the best way I can describe my docker usage is as a simple and agnostic service manager. Let me explain.
Docker is a container system. A container is essentially an operating system installation in a box. It’s not really a full installation, but it’s close enough that understanding it like that is fine.
So what the service devs do is build a container (operating system image) with their service and all the required dependencies - and essentially nothing else (in order to keep the image as small as possible). A user can then use Docker to run this image on their system and have a running service in just a few terminal commands. It works the same across all distributions. So I can install whatever distro I need on the server for whatever purpose and not have to worry that it won’t run my Docker services. This also means I can test services locally on my desktop without messing with my server environment. If it works on my local Docker, it will work on my server Docker.
There are a lot of other uses for it, like isolated development environments and testing applications using other Linux distro libraries, to name a couple, but again, I personally mostly just use it as a simple service manager.
tldr + eli5 - App devs said “works on my machine”, so Docker lets them ship their machine.
I’m not sure where you heard that info about the keys, but it’s not right at all. In fact, suyu went the ryujinx way and makes you provide all the keys and the firmware yourself, whereas yuzu only required the keys.
Suyu has done a lot to remove the problematic code and restructure their documentation. It would do well for people criticizing them to first go see what they’ve done. The suyu devs themselves said that the DMCA request didn’t even come from Nintendo, it came from gitlab automatically because they forked a repo that was taken down.