Portainer
Web GUI for Docker, Docker Swarm, Kubernetes and Nomad — Anthony Lapenna, 2016. "Cockpit for container hosts".
Community Edition free, Business Edition commercial with RBAC, OAuth, edge management. Common choice at home labs (running docker-compose stacks with a UI), MSPs, and edge deployments where fully managed K8s is overkill.
Competitors: Rancher (more K8s-centric), k9s (terminal-only), Lens (desktop GUI), Yacht (lighter hobby alternative). Portainer dominates the "small-team-with-docker" segment.