This has been posted on Reddit and Facebook, so I wanted to let others here know too. There is a discord group set up for discussing travel plans between people attending the Fan Festival in Germany, as well as meet ups.
The Frankfurt locals have made a Google map of the area with suggested restaurants and locations of hotels some are staying at. There's also information on train networks and advice on reaching the hotels from the airport.
I don't know if putting a link here in the post is okay with the owner yet, or okay with forum rules so, if you're interested in joining send me a PM or ask here and I'll forward you a discord invite. See you in Germany!