A lot of Eastern European countries should still have large stockpiles of old Soviet military gear. Including Germany, which inherited the entirety of East Germany's armed forces, including top notch MiGs (not the watered down export versions other countries where using). Some of those stockpiles are provided to Ukraine, including ex. DDR APCs (didn't know Germany still had those, I supposed they have been scraped a long time ago...). Which makes sense, those Soviet weapon systems are much easier to use for Ukraine than NATO gear.