Is there any evidence to suggest that kubb might have been played in the Viking Age, or was it just associated with Viking history to promote it? If so, who invented it, or when did it originate?
I have attempted to do research on the history of Kubb, and although there are claims of people having played games called Kubb before 1990, sometimes as far back as the early 20th century, none of these can be verified, and certainly no description of such a game and it's rules survive. The first commercial Kubb games appeared on Gotland in the late 1980's or early 1990's. They were sold as ancient Viking game.
Gotland has a long tradition of local games, many who date back very long, at least to medieval times, and in some cases they could very well date back to the Viking age. For example, one of the traditional local games are stock tossing, also popular in Scotland. It's perfectly possible that this game was spread from one area to the other during the Viking age, as this is the last pre-modern time both areas would have had frequent cultural exchange.
So therefore, branding Kubb as a viking game would have seem plausible to tourists, although natives like me wondered why on earth they never had heard of Kubb before 1990, if it was a traditional game from Gotland.
The complete lack of any sort of reliable evidence of Kubb before 1990 does lead to the conclusion that Kubb does not have any Viking roots, and that the claims are simply made up as a marketing ploy.
Games where you throw sticks at some sort of target to make it fall over are documented since at least medieval times. However, almost all of those games are not side-based, but turn based. Skittles and Bowling are examples of games have evolved from those. It seems Kubb is another modern development.