> though it doesn't have CloudKit support out of the box

There is no CloudKit support for GRDB available anywhere except for via this SQLiteData package

"Harmony" was an experiment in adding it to GRDB on iOS 17+ but reports claim that it's broken. SQLiteChangesetSync is another earlier experiment that is unmaintained

I don't think it is an experiment, AFAIK it is used in a widely used application by the author.