One might expect that to be the case, but I haven't yet seen a case. Before I 'swapped' last year I must have looked at literally hundreds of tariffs. The conditions of a good few said things like "you must have a smart meter", but I don't recall any supplier saying that "it didn't count" if you already had a 'smart' meter!I vaguely recall having seen tariffs that are only available to those without "smart" meters, and a condition is that you agree to have them fitted. Those will be by way of helping the supplier to meet their targets for fitting "smart" meters.
Kind Regards, John