Here are two unofficial Discord servers with active fanbases with lots of information, fan content, and off-topic conversation with fellow Mahou-yome fans.
JungPhoenix (Jason)'s large, open and active community
This is a very large server with no verification process. It is very active and has a lot of official contents linked in it, as well as a lot of high-quality fanworks; like fanfiction and art. Everyone is welcome, and we can assure that is the right place to both share and receive fan content, as well as finding information that's not currently on this fandom wiki of Reddit.
Riva's 18+, safely moderated
It is a small and wholesome Mahou-yome server with ”ddlg, dating, cosplay and roleplay". I can assure you, everyone on this server is like good friends. It’ sadly a little bit quiet, and that's why we hereby invite you to join. but... BEFORE JOINING READ THIS:
It's an 18+ server. You will need to prove your age with a Government ID. Drivers License, State/Province ID, and Passports are acceptable. School/College IDs are not. You'll need to provide evidence to a moderator, a picture containing your face, ID, and discord name written in it, on paper. Everyone needs to be verified in order to be apart of this server to keep stuff safe and that we also know who we let in this server as this is a safe place.