Ah my hometown. Unfortunately I don’t visit Flensburg often enough to have found any more interesting beer places - you will be able to sample Flensburger Pils just about everywhere though
The Rum and Sugar mile is quite interesting. The tour itself is a historic walk through town, but you should also pass by Johannsen Rum where you can sample and buy their blended rum. The other remaining producer is Braasch, actually a wineshop which has specialised a bit in rum again.
If the weather is bad get a “Grog” in one of the restaurants (its just a hot toddy), I assume it soon will be rateable here on the site
Cheers @Jonas, we will most likely hit the brewery first and then walk back down through the town using the Rum and Sugar Mile. Can’t find anything in English about it though, looks really interesting. I will print this off and use my pigeon German to try and understand it all.