I have started to update the FW on some Tasmota flashed plugs and this has resulted in the creation of a new set of sensors. The old ones didn’t have the correct device class etc.
The old one is sensor.XXX and the new one sensor.XXX_2
Is there a way to delete the old one and recreate the new one without the _2 as a replacement?
Open the sensor.xxx, select the tab “Settings” and you should have a “Delete” button in the bottom left.
After deleting the sensor.xxx you can open settings of sensor.xxx_2 and change the entity ID to sensor.xxx.
Delete is Greyed out.
On updating the Tasmota Firmware, it has forced the discovery option on, so the HA Tasmota Integration has found it, but the MQTT integration (the old way) is still finding it as well.
No way to delete the Device from the MQTT Integration 
[edit]
Ah, seems I just needed to be patient and let HA decide it no longer existed. Delete is now available.
Shame no way to do a bulk update or the name
[edit2]
And HA has found all the MQTT ones again on restart…
It may be because of the MQTT settings on the device;
[edit3]
Just keep clicking things 
On the Device page I can delete from MQTT by clicking on the 3 dots…
I’ll do another then write a full solution 
Use Mqtt explorer to delete old discovery devices
