Nevermind. Reading the libcanard-header, anonymous nodes seem to be a no-brainer since
#define CANARD_NODE_ID_MAX 127U
...
/// This value represents an undefined node-ID: broadcast destination or anonymous source.
/// Library functions treat all values above CANARD_NODE_ID_MAX as anonymous.
#define CANARD_NODE_ID_UNSET 255U
Also, this forum.opencyphal.org/t/automatic-configuration-of-port-identifiers/840/3 discussion was most helpful and closely related to my problem.