Even if you don’t have documents, citizenship restoration specialists can search Lithuanian archives. I contacted specialists, and they found records about my great-grandfather in old registers. This was enough to obtain lithuanian citizenship. The main thing is to provide accurate information: name, place, and year of birth. In some cases, even old church records or children’s birth certificates are suitable. After restoring citizenship, you will receive a Lithuanian passport and all the benefits of an EU citizen. Everything is done remotely, so you can do this from anywhere.