If you are using Alpine, the easiest and safest way is to install the specific "SUID-enabled" version of the BusyBox applets. Run this command as root: "su: must be suid to work properly" => How to get rid of it
The error message "" is a common hurdle for users of embedded systems, rooted Android devices, and lightweight Linux distributions like Alpine. It indicates that the su (substitute user) command lacks the necessary SUID (Set User ID) permission bit required to elevate privileges to the root level. Understanding the SUID Bit busybox su must be suid to work properly
After setting SUID, test: