I was using mybb and they had this option to add a custom field to the inscription process and option to display it on their profile page
e.g : a question What games do you play? + checkboxes to choose from.
I can look into doing/helping with something like this! I think you might need a discord bot in the server to grab the ranks on discord. (I could be very wrong) I too am looking for this functionality and other things like profile picture, and status.