The thing is, the "software" actually is open source, so you can tell how data is requested from your smart ID. The german government ID has an explicit function for age verification that does not provide any personal information.
https://github.com/Governikus/AusweisApp2
However it is probably hard and costly to get certified to use any of those functions as a service provider.
I have seen https://opencollective.com/ used a lot to collect donations in a transparent way (also supporting crypto payments). Maybe that is something you want to look into as well.