Despite not being mentioned in the 2024.10 core update notes, the UI Template integration seems to have been deprecated. Updating my server core to 2024.10 broke all of the sensors created under this integration. Restoring the previous version fixed this and I was able to recreate the sensors with Helpers/Template facility. One of the side effects was that in the new sensors which provided time related strings, assigning unit of measurement (h or h:m) was no longer allowed which simply means that the history display is just a bar graph rather than a numerical graph. Apparently the UI Template integration allowed this but perhaps by breaking some Python rules.
While recreating the very last sensor, I decide to disable it first in the hope that HA would not append the dreaded _2 to the entity name. Needless to say that did not work. A curious thing did occur however. With the last sensor in the integration disabled, the integration disappeared from the integrations list. There was no way to delete the original sensor from the integration. After much trial and error, looking for the sensor definition in the HA file structure and much restarting of HA, I was giving up and editing my dashboards to reflect the _2 entity. Trying to remove the integration through HACS proved pretty fruitless. In the end, I simply reinstalled the UI Template integration, created a bogus sensor which now allowed the removal of the errant sensor. Of course the integration disappeared fron the integrations list but ripping it out is a task for another day.