It seems to me that org-capture requires templates to start with a heading (*). Can I not have a template like:
("d" "Daily Tasks" entry (file+datetree+prompt "daily.org") "- [ ] %?")
that does not start with a *.
You have to change the third element the template ("entry type"). From the help:
type The type of entry. Valid types are: entry an Org node, with a headline. Will be filed as the child of the target entry or as a top-level entry. item a plain list item, will be placed in the first plain list at the target location. checkitem a checkbox item. This differs from the plain list item only is so far as it uses a different default template. table-line a new line in the first table at target location. plain text to be inserted as it is.
For a checkbox you want
checkitem instead of