Is this the same information on the "built for mars" website? https://builtformars.co.uk/banks/

I think the summary is that the challenger banks are better because they have been built from the ground up to have a good user experience. The only problem is that great user experience comes at a cost: the development and running costs are expensive and good user experience can hinder the ability to up-sell to the products that make traditional banks the most money.