The document at /products/devtools/technicallibrary/m/files/1607 states on page 5 that the credentials to use is avnet/avnet. When using a display, a login banner is not shown (despite the doc) and a wayland session is opened as root so users may not notice the wrong credentials.
When attempting to login on serial console OTOH avnet/avnet is just wrong, probably refers to older images. The only enabled account is "root", with password "avnet". There is a non-privileged "user" account, but its password is disabled, and it does not appear to have any use in the default configuration.
