The alternatives can be categorized into these 4 categories
Container as a Service (CaaS): Options in this category are services like AWS Fargate and Azure Container Instances. These cloud services manage the complexity of managing containers at scale and eliminates the need for managing or running Kubernetes.
Managed Kubernetes services : Popular choices in this category are Google Kubernetes Engine (GKE) and Amazon Elastic Kubernetes Service (EKS). These services abstract the complexity of designing, deploying and managing Kubernetes. Underneath the engine is Kubernetes, so you will still need Kubernetes experts in the team
PaaS using Kubernetes: Many third party providers offer Kubernetes as Platform Services like OpenShift Container Platform and Rancher, they offer simple ways to manage Kubernetes cluster and abstracts all the complexity and offers simple way to manage containers.
Container Orchestration Tools— Docker Swarm and Nomad are two examples of popular, capable, mature container orchestrators, which are much less complex to use and manage than Kubernetes.