Comparing HA-cluster platforms for my usecase

Honestly, from a pure ROI and operational load perspective, it doesn't sound like container runtimes at your current datacenter is the right solution for this problem.

From an operator perspective, a container system makes sense when there are tenancy and heterogeneity problems that are hard to solve with VMs/VPSes, and the plant is at minimum dozens of nodes in size. Running any container infrastructure in an HA manner is a lot of work, and there are a lot of corner cases that require dedicated, specialist attention. The need has to be large enough for it to make sense to make this investment.

The plant as described, with redundancy, can run on a handful/dozen VMs/VPSes. It needs some careful architecting to achieve desired levels of availability, but the patterns for managing databases and stateless apps on VMs for HA with, say, 3x scalability, are pretty well established.

There is still a lot of discovery happening in the container world. With Kubernetes especially, every quarter there is a whole new release with new corner cases to discover.

Of course, it's really fun to learn about it, but it's still at the state where it's marvelous to see it working, not boring.