Apparently Triss married Eskel in a "non-canon" short story that takes place after the events of the canon stories. Does anyone know of an English translation of this story, "Coś się kończy, coś się zaczyna"? The title translates to "Something Ends, Something Begins", the same words Geralt says to Dandelion at the end of the first game.

I'm not sure if there is a translation, may be only fans one. I have read a Czech translation of this short story and I think that it is not important for main story line in Saga and games. This short story is mainly fun and comical. It describes one big party at Geralt and Yennnefer marriage. As noted in the story Triss and Eskel had been seen going to garden arbour in the night hand in hand. Lot of comical situation at the party had been caused by guests of poor reputation. They had been invited by Dandelion (Marigold in Czech, Jaskier in Polish). There also appears Ciri (as Geralts and Yennefer daughter) and a knight of king Arthur (the last book of the Saga - Lady of Lake).

Isn't that one of the adventures added to the enhanced edition of The Witcher?

It`s joke

The story was a wedding present from Sapkowski to some friends. It's pleasant but non-canon--an alternate universe sort of thing. The wedding mod for TW1 is a different story entirely, also non-canon and just for fun.