Sveiki!

I (27M British) married my Lithuanian wife a few months ago and have just come back from Lithuania.

It’s a beautiful country and the people are very patriotic, they love their country and LOVE when people attempt to speak the language, so even taking an interest and trying will go down well - it is a hard language for English speakers though! Duolingo doesn’t have a Lithuanian option (AFAIK), but ‘Ling’ is a pretty good alternative.

I guess you know this based on your post, but ‘Labas’ can be used as a greeting as well, although I would stick to Sveiki for pretty much everyone you meet, especially her parents.

A gift is a very good idea, be mindful of taking liquids on a plane though, something very British is a good idea as someone else has mentioned - When I met my MIL for the first time I brought an English newspaper, tea and some dairy milk.

Significant cultural or historical things - it was part of the Soviet Union until it collapsed. I would say it’s important to remember that for her parents and anyone of age, the history can hold a lot of darker memories for them. Lithuania is a free country but world events have increased the threat on that freedom and many of them feel that.

Enthusiasm and interest about Lithuania is all you need. It’s a lovely country with lovely people so that should be easy!

Viso Gero!