In other words, will he or she be of European nationality?

Will probably resolve based on what flag is next to their name here:

https://en.wikipedia.org/wiki/Catan#World_Championship

If you have questions you can ask. Turkish counts as European, I suppose.

Tournament will probably be held in 2024.

I won't bet.

"The next international event will be the 2025 CATAN World Championship. Date and location are TBA."

https://catanevents.com/players/champ/