There are few importers available which have been opensourced (look at the Actual's github org), I have only tried one during migration from greedy YNAB. There

There are few importers available which have been opensourced (look at the Actual's github org), I have only tried one during migration from greedy YNAB. There is also an API which works quite well. I am using it to import transactions from Revolut. So no Open Banking yet, but afaik it's painful to get in the UK anyways