By the sixteenth century, the Holy Roman Emperor Charles V suffered from a massively protruding jaw, with a mouth agape and a stubby tongue slurring his speech.

Source: https://www.newyorker.com/magazine/2023/05/29/the-world-a-family-history-of-humanity-simon-sebag-montefiore-book-review

In 1521, Martin Luther (1483–1546) made his decisive break from the authority of the pope and the Holy Roman Emperor, following the Diet of Worms.

Source: https://www.christiantoday.com/article/the.other.reformation/140922.htm

Not only does this point toward a Witch Hunt setting in Germany, within the time of the Holy Roman Empire, but it's also worth noting that the mysterious language seen in the trailer isn't Isu either.

Source: https://gamerant.com/assassins-creed-hexes-setting-germany-witch-hunt-brotherhood-impact/

Players need to ensure Matilda's Bishop's endorsement, The Pope's friendship, and Matilda's placement within Kaiser Heinrich of The Holy Roman Empire's good graces.

Source: https://gamerant.com/ck3-duchess-matilda-give-dog-bone-achievement-tips/

When the bold Richard was captured, the Holy Roman Emperor was paid 150,000 marks for his release.

Source: https://www-tmp.thenational.scot/politics/23673734.john-drummond-british-royals---mad-bad-dangerous-know/?ref=rss