Got this error on my home page.
Managed to pin it down to the Slideshow Addon.
When I add the default content to the slideshow, this error appears:
count(): Argument #1 ($value) must be of type Countable|array, string given
The error disappears when I add an Item within that content with the + Add Item button.
This might be related to SP Page Builder Translate, since it only happends on my secondary language.
Perhaps this info helps someone.