If you're looking for a simple Kubernetes alternative, take a look at the HasiCorp stack. I use that in production and it's easy to set up and maintain.
I use k3s in production, and it is great. But as far as daily use, it is not any simpler than kuberenetes. Initial setup and clustering is a breeze with k3s. But after that, you are mostly just working with the same k3s api as a full kuberenetes setup.
k3s is kubernetes. Simpler to install and get a cluster running and much smaller, but still kubernetes, with an identical feature set and API. That is part of the point of kubernetes, that it is a standard and anyone can implement it, with Google's original implementation only being a reference, not canonical.
They don't mention that this was accomplished via k3s, but I happen to know it was because it was colleagues of mine that did this. The point of being able to do something like this is you can deploy a completely identical stack of admin/controller level software to systems running in data centers and systems running in airplanes. As long as they can run kubernetes, you're good to go, and with k3s, just about any piece of hardware can run kubernetes. This has huge implications for defense because it means you can develop and test software that isn't directly responsible for specialized hardware control without having to build emulators or lab equipment identical to what is installed in the actual weapons platforms. You just need to ensure they can both run kubernetes.
It doesn't have to be kubernetes, obviously, but you get the advantage of a fairly rich ecosystem that includes things like k3s, which doesn't even require bash or a shell at all to work.
The YouTube channel [0] has plenty of introduction videos, but I find the documentation [1] to be the best place to start. You should set up Consul (service mesh) first, followed by Nomad (orchestration), and Vault (secret management) if you need it. The only thing I initially struggled with was the systemd-resolved config on Ubuntu, to make the service discovery work. I plan to write an article about it, should I ever find the time for it :)
Btw. the cluster consists out of three servers on Hetzner [2] and runs our web analytics platform Pirsch [3].