Hello! I recently encountered an issue while installing Flarum, and I thought it might help to post the troubleshooting steps.
I was getting HTTP 500 Internal Server Error. I went to the config.php file and set debug as true.
Presto! It showed me the issue I was having. If you are having issues with flarum, try enabling debug before posting here and see if you can solve it yourself!
If you encounter the same issue, post here and I will see if I can resolve it