Site using this plugin - https://www.mathelounge.de/
Basically this is a paypal donation link plugi. when user answer the question then his/her donation link appears below his/her answer.
TAKE A LOOK
Screenshot of the plugin feature
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask in English.
To report a bug, please create a new issue on Github or ask a question here with the bug tag.
If you just want to try Q2A, please use the demo site.
May 7, 2020: Q2A 1.8.4 released!