We seem to be stuck with plugin-annotation v1.3.0 and chartjs v3.7.0 where following example for a line chart with multiple datasets works with multiple annotations.

https://codepen.io/dbauszus-glx/pen/MWOjGzw

Upgrading plugin-annotation to v2.0.0 causes following TypeError: Cannot set properties of undefined (setting 'display') at resolveLabelElementProperties.

Upgrading chartjs to v3.9.1 causes a different TypeError: Cannot read properties of undefined (reading 'lastIndexOf')

The same error persists with chartjs on v3.9.1 and plugin-aanotation on v2.0.0