I think you might have misunderstood that page. The standard and universal way to deploy Kubernetes on to either your own bare metal or any cloud provider is to use kubeadm. However, if you would like a simpler and more automated solution and/or one backed by a vendor, you are welcome to pick any of the hosted platforms, distributions, or installers. CNCF has certified 70 conformant solutions: https://www.cncf.io/certification/software-conformance/
> Even if I never moved out of the big 3 (AWS/Azure/GCloud), the migration process could be painful since their Kubernetes may introduce further lock-ins for logging, monitoring, and so on.
If you choose open source solutions for logging and monitoring like Fluentd and Prometheus, then you can avoid locking into anyone's value added services and remain completely portable. If you decide to go with a vendor's solution, you may trade convenience for higher switching costs.
[1]: https://kubernetes.io/docs/setup/pick-right-solution/
Disclosure: I'm executive director of CNCF and run the conformance program.