Small addition on helpers, since most of my logic lives in them and they behave slightly differently from device entities.
Helpers made through the UI — template, statistics, derivative, filter, min/max, utility meter — go through the same generation, so they picked up the prefix too. The wrinkle is that the name a helper gets depends on what was set at the moment you created it. Set the area or the related device afterwards and you can end up with a helper whose ID reflects a state that no longer exists, sitting next to one you made ten minutes later that looks completely different. Around the 2026.6.1 point that produced some genuinely strange ones.
Also worth checking before you do any manual work: this was walked back to the extent that the pattern used to generate new device and entity names is now something you can configure, rather than being fixed. So depending on which version you are on, the answer to "is there a setting I missed" may have become yes since the release that gave you the doubles. Check that first — it is cheaper than renaming anything, and it changes only what gets generated from now on, which is the safe half.