AlmaLinux is a downstream fork of Red Hat Enterprise Linux (RHEL), while CentOS was originally a community-driven and completely free version of RHEL.
AlmaLinux is developed and supported by the company CloudLinux, which is well-known for its expertise in the hosting industry. On the other hand, CentOS was previously supported by Red Hat, but starting from CentOS 8, it is now sponsored by the CentOS Project.
AlmaLinux aims to be binary-compatible with RHEL, providing a stable and secure replacement for CentOS. As a result, AlmaLinux releases are closely aligned with the respective RHEL releases. In contrast, CentOS follows a rolling release model, where updates are continuously released rather than having major version upgrades.
AlmaLinux offers long-term support (up to 10 years for major versions) similar to RHEL, providing stability for enterprise environments. CentOS provides five years of support for each major release.
CentOS has historically been known for its strong community involvement, with active contributions from users. While AlmaLinux encourages community involvement, its development is primarily driven by CloudLinux.
Regarding cPanel and WHM, it is highly recommended to update the OS to AlmaLinux as per the warning provided. cPanel and WHM work closely with the operating system, and using a supported and recommended OS ensures compatibility, stability, and security. While cPanel may continue to work on CentOS for a period of time, it is advisable to plan and migrate to a supported OS like AlmaLinux to continue receiving updates, patches, and support without any interruptions.