Source: https://blog.tiga.tech/deleting-devices-and-entities-in-home-assistant/
One of my major bugbears in Home Assistant (HASS) has always been that there’s no proper way to completely delete a device or entity.
It seems so odd to me that there is just no functionality beyond “disable”.
Note: It’s been pointed out to me that this is only true for entities which are available. For those which are marked “unavailable”, there is an option to delete. I will keep this up though because I’m sure it will still be useful for someone!
However, it’s not quite true that there’s no way to delete them… It is possible, but it can also be dangerous.
Entities and devices are stored in /config/.storage/core.device_registry and core.entity_registry respectively. Depending on the type, they have also have an entry in core.config_entries.
Below is the process to entirely remove a device and/or entity in Home Assistant.
Please note that I cannot take any responsibility if you break your HASS installation.