Data has a range of misc items called "T_Com_Key_XX". Their chief use is to copy them into new objects if you want a key to have a particular look. In special cases you might want generic, non-useable keys to clutter a location - TR has one of those, the daedric ruin Ashinanibibi, where you can find a pile of keys left on the altar. That's fine, because the context makes it clear that this is for worldbuilding purposes.

However, there were a handful of other places that had just one or two keys lying around somewhere (also, one floating in the void), and that's very bad from a gameplay perspective, because players will inevitably think there is something nearby they can open with it. There might have also been the idea of a "treasure hunt" at some point, where keys would open containers in totally different locations (vanilla also had that, though barely implemented), but if something like this ever gets made, it should still be a TR-unique key, not using the T_Com generic entries.

So I've removed all the generic keys in Mainland except from Ashinanibibi. I also removed the levelled list that would spawn a random generic key (and should probably get deprecated) from all NPCs that had it, mainly bandits and corpses. The only exception is Heran Llothar, because I edited this NPC in another fix (https://www.tamriel-rebuilt.org/bugtracker/you-can-find-84-bottles-skoom...) and already got rid of it there.