Perhaps the pull request "add way to set default ordering for child pages in wagtail #11290" which landed in Wagtail 6.0 helps:

• Add ability to modify the default ordering for the page explorer view (Shlomo Markowitz)

Usage in your page model:

class MyPage(Page):
    # via attribute [1]
    admin_default_ordering = "ord"

    # or via method [2]
    def get_admin_default_ordering(self):
        return "ord"

[1] https://docs.wagtail.org/en/latest/reference/models.html#wagtail.models.Page.admin_default_ordering
[2] https://docs.wagtail.org/en/latest/reference/models.html#wagtail.models.Page.get_admin_default_ordering