I did this by modify the funtion qa_get_request_content in the file \qa-include\app\page.php like below:
redirctor the home page to question.php
you can see the demo :OGeek|极客中国-Developer Community
May be some day i will make a plugin to do this
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask here, 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.
April 20, 2021: Q2A 1.8.6 released!