Issue on getting the user submitted input data from Adaptive card posted via MSTeams Graph API
Solution 1:
It is not possible to get Adaptive card input with subscriptions. Instead you can have a Bot having teams as a scope in manifest, which will send an adaptive card and you can get the input from there. That is much easier.
We have sample created in c_sharp, here is the link
https://github.com/microsoft/BotBuilder-Samples/tree/main/samples/csharp_dotnetcore