It always-all yr, and much more often used to be possible to do this trip by using sep. buses on PL and SK side and walk across border. I guess that is still so. On PL side: the usual minibus, runs (ran?) fairly often, like ev 20/30 mins-may vary with season. IF start this way-have some zlotys to pay and not more, as you cannot use them further on. Ask driver to point out border, as its a side rd not directly visible. Walk over. On SK side a less frequent (and on sat sun just a very few) local SAD buses: sad.sk. Pay driver in€. Ends probably not Poprad but Stary Smokovec-may vary with trip. Times can be found via that side (sorry, I forgot exact name for this point-something with ´hranica´=border). IF not too long wait on SK side doable in <2hr. StSm is on those funny little tram-like trains where your pass is also valid as its all ZSR

It is no problem to get to the border by minibus, just head to Morskie Oko and get off a little bit earlier or walk back from the parking space. 
This buses run frequent. Cash only (if nothing changed since Corona, but highly doubt that you can pay by card)

Walk across the border bridge. Buses on other side are very infrequent or sometimes not at all running. But there are (at least on days with nice weather) MANY cars. So hitchhiking with general precautions is very straightforward.