Red Hat is an IBM-owned open source software company offering Red Hat Enterprise Linux, OpenShift and Ansible for hybrid cloud, automation and enterprise infrastructure.
SUSE is a German open source software company offering SUSE Linux Enterprise, Rancher Kubernetes management and edge solutions for enterprise and cloud-native workloads.
Canonical is the UK-based company behind Ubuntu, offering Linux, cloud, containers, IoT and enterprise support services, with Ubuntu Pro subscriptions for security and compliance.