As soon as it becomes available in upstream Debian.
https://repology.org/project/chkrootkit/versions
https://tracker.debian.org/pkg/chkrootkit
https://salsa.debian.org/pkg-security-team/chkrootkit
rkhunter is already the latest version
https://repology.org/project/rkhunter/versions
Why is chkrootkit important?
Using rkhunter alone does not guarantee that a system is not compromised. Running additional tests, such as chkrootkit, is recommended.