If you specifically need version 12.6, it is primarily available through software archives rather than the official IObit site, which promotes the current version (v18).
Advanced SystemCare Ultimate 12.6 is a legacy version of IObit's all-in-one security and performance utility. While you can still find downloads for this specific version from third-party repositories, it is generally recommended to use the latest version to ensure you have the most up-to-date virus definitions and system optimization tools.
: Sites like Uptodown and FileHippo maintain historical versions of Advanced SystemCare Ultimate.