This doesn't really mean much on account of the iOS ecosystem only supporting the latest two OS versions in their apps as a general rule. Once you are behind 2 versions, your device becomes quite useless at that point
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No huge deal breakers _personally_ as I don’t need banking on my phone anyway (I have an iPad at home, and also checked that the banks offer authentication devices like TAN generators if I really need to get out of the iOS/Android ecosystem).
Apple Pay still works fine.
I hope that small phone has a long life ahead of it still :)