A few hours after this change, I checked again and the order went back to decreasing activity instead of decreasing creation (I’m the only administrator, so I know nobody else changed it).
Strangely, that’s only on desktop (I’ve checked on multiple accounts and different browsers). On mobile, topics do show up ordered by creation.
Even more strangely, when I add ?order=created to the URL and visit it, other logged in users see the right (default) order.
Anything else I can try?