I can't speak for Dresden, but Potsdam definitely still has them! They're pretty easy to find during peak hours. Frankfurt(Oder), Cottbus and Brandenburg still have them, but they're scheduled to be withdrawn from all three over the next couple of years. The Schöneicher Straßenbahn from Friedrichshagen S-Bahn also still uses some Tatras.
If you haven't done so already I really would recommend a visit to the Woltersdorfer Straßenbahn which runs from Rahnsdorf S-Bahn. It still uses old Gotha cars from the early 1960s, but these are also scheduled to be replaced in the near future.
Interesting, I didn’t think Potsdam would still have them these days. I last visited quite a few years ago and didn’t manage to track one down, but I don’t think I was there during peak times.
Same for Brandenburg - I visited the city on a Sunday (big mistake as everything was shut!), and it was just a skeleton service on their tramway with just modern stock in use.
I have visited the excellent Woltersdorfer tramway before - incredible it has survived so long with vintage stock. I will be hoping to revisit during my trip.
Annoyingly I’ve been to Berlin a few times before, when they still had Tatras - but I didn’t make the effort to track them down as I wasn’t really into trams back then.
I really wish there was an equivalent to bustimes.org for public transport in other countries. The nearest I’ve found is the Brno, Czechia live map which includes fleet numbers.