Somewhere out there, there's probably an older thread about this, but I don't want to be accused of necroing it, so...
My recollection is that in the past, there was a way to delink your account from Steam by buying a new account directly through the ESO site and then, I believe, just logging in with your character ID from the old Steam account. But it seems like there were some additional steps beyond that, maybe? Does anyone know whether it's still possible to do this, and if so, what the exact steps are?
With the Black Fredas sale, the base game is only $5.99 (US), so it seems like a good time to get that done.