The method for integrations to provide translations for states of its entities under other integrations, for example to translate an integration's sensors was changed in November 2022, and support for the old method will be removed in Home Assistant Core 2024.5.0.
Once Home Assistant Core 2024.5.0 is released, integrations can no longer use custom device classes together with a strings.<platform name>.json file. Instead, entities must set the translation_key property on an entity and include that translation_key in the integration's strings.json.
The following example strings.json is for a Moon domain sensor entity with its translation_key property set to phase:
{
"entity": {
"sensor": {
"phase": {
"state": {
"new_moon": "New moon",
"first_quarter": "First quarter",
"full_moon": "Full moon",
"last_quarter": "Last quarter"
}
}
}
}
}
For more details, see the translation and entity documentation.