Great use case! Worked on exactly this a decade ago. It was Hard™ then. Could only make so much progress. Getting this right is a huge value unlock. Congrats!
Even though it's 2024, banks, financial institutions like insurance companies etc. tend to be _very_ cautious with valuable documents involving customers. There are also regional regulations that prevent things like patient data being shared with _any_ 3rd parties. Even one of the big 4 oil companies that I've dealt with as prospective customer - very strict rules requiring on premise solutions.
The good news is many are using things like Kubernetes and OpenShift internally, so it should be possible to port what you do on AWS to on-premise.
Better still if it can then become a source of truth for further departures from reality.