It's possible to run the services without Kubernetes, but official ESS Community uses Kubernetes.
ESS Community works ‘out-of-the-box’ on a single machine or existing Kubernetes cluster using the provided Helm charts.
Self-hosting a Matrix server for 5 years
Is (Matrix) Element Server Suite overkill for a dozen users?
Disable power to USB hub
Resurrect your old Android phone - aggregated list of 1100+ devices and what OS you can install on them
I knew of some of these issues with the protocol, but this article definitely gives an impression that Matrix was built as a "cool protocol" first, with messaging applied on top as an afterthought.