There should be no barriers to accessing a donor's bank accounts in the event that they lose mental capacity, however it is slightly trickier if they are existing customers with some app-based banking providers.
Chase, for example, requires attorneys to register and manage accounts via telephony – and therefore does not grant access to the donor's app.
For other providers such as Starling Bank, it is required that attorneys must be existing customers or open accounts with Starling before they can access the accounts.