This site is best for current info: seat61.com, but read full story, as the updates come at the end.

The train LT->LV has been cancelled since covid outbreak and not returned.

From PL to LT it is weekends only tiny diesel by {PolRegio-SUMMERtime only-said to end 1st week sept. Bialystok-Suwalki-Kauno. FRI/Sat TO LT, Sat+sun-mornings- FROM LT to PL.

You will loose many hours by doing this train shuffle compared to the many direct buses/autokary Warszawa-Vilnius. There was also a recent long thread about how to use pass in Lietuva=Lithuaina=LT/Littauen. Find and read it to be informed. Many passholders tend to be a little bit stubborn in using trains only-in some areas this will simply just be an annoyance (there are some special forums auf deutsch-die für jene Bahnverrückte alles erklären und gleichgesinnte besorgen)

Thx for your very helpful reply, I really wished there was some information about that cancelled train connection on the interrail website. There seems to be so much completely outdated information!

So now I will be thinking about/trying to get a bus from Klaipeda to Riga.

Danke für die Hilfe :-)

@mcadv I wish you'd also do that...

… because then you'd know that this is incorrect. This train runs during the weekends until 10 December and after that, there's a daily service (timetable still to be confirmed).

Providing wrong information is his hobby

I just used the Bialystok to Kaunas train on Friday