One of the maintainers of KMyMoney, an open-source personal finance software. We looked into (https://invent.kde.org/office/kmymoney/-/issues/21) leveraging one of the 3rd party aggregators like yours to allow users access their data. The conclusion was that being an open-source software was a no-no for all of them, unless we were willing to sign our binaries with certificates (that the aggregators require) and distribute the software as such. All of that obviously aside from the cost of the service itself.
Do you see if this could be made possible with Nordigen?