For anyone going to the Euros basing yourself around the Rhur, the Bermuda3eck in Bochum is genuinely as good as you'll get for boozing in that region. Might not be as packed with other fans as Dusseldorf for example, but that might be what you're looking for. Bonus of the best beer in the region too
If you're there swing into Mandragora at the end of the main drag, owner is a massive Leicester fan and will give you a big welcome.