I’m moving my book from Apple to Libre, but the footnote numbers are consecutive chapter after chapter. I assume it is because there must be a way to start each chapter anew, but can’t find a way to do that.
Without much information, it is impossible to give a definite answer.
Which application is the source app? Apple is a company name, not an app name.
How do you “move” your book? I.e. how is it loaded into Writer?
Writer is based on styles. Specific paragraph styles will inform Writer that a chapter change is occurring. Also, footnotes are an independent matter: they can be numbered continuously, chapter per chapter or page per page. This is user-selectable.
If you don’t know what Writer styles are, read the Writer Guide for an introduction.