I know that European Union member states are obliged to provide public sector data, including on government spending, based on the EU Directive 2019/1024 but as you mentioned, the implementation and quality of data provided depends on each country.
One suggestion I have is to consider creating a mobile app for Diofanti to make it more accessible to people. Also, you could provide APIs to allow other developers to build on top of your processed data.
Keep up the great work!