I doubt very much that it is possible for this practice to be legal, i.e. to condition the services of an European bank of the existence of a contractual relationship with a third party, which is non-European.
Nevertheless, nobody has enough spare time and money to challenge legally such banks.
Now I do my operations mostly through other banks that still have browser-based online banking, but I have not closed yet my last account at such a Societe Generale subsidiary, because I have regressed to use an antique SMS-based substitute for online banking, which is good enough for that account, which I keep only for a credit card used mostly for shopping in supermarkets or the like.