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InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
[ActualBudget](https://actualbudget.org/) supports open banking via [GoCardless](https://gocardless.com/). GoCardless (previously nordigen) deal with meeting the Open Banking standards and connecitng to all the banks and provide you with a fairly straightforward API for it.
https://github.com/Gnucash/gnucash/pull/1794
Note the full API may be accessible via a cli interface.
The above work will be merged hopefully soon.
Actually https://github.com/dpaetzel/buchhaltung could fit your needs. Just found it because I thought that someone must have built this already.