k3s is intended to be a fully compliant Kubernetes distribution with the following changes:
Legacy, alpha, non-default features are removed. Hopefully, you shouldn't notice the stuff that has been removed.
Removed most in-tree plugins (cloud providers and storage plugins) which can be replaced with out of tree addons.
Add sqlite3 as the default storage mechanism. etcd3 is still available, but not the default.
Wrapped in simple launcher that handles a lot of the complexity of TLS and options.
Minimal to no OS dependencies (just a sane kernel and cgroup mounts needed). k3s packages required dependencies