Problem/Motivation
Currently, there's the ability to use the Register form mode (created in core user module) on the /admin/config/people/accounts/form-display page, which when enabled, will be automatically used when viewing the user register form. There isn't any control in what form mode should be used for the user register page and this means that administrators with the permission 'Administer users' are restricted by the same form display.
Proposed resolution
Add the setting "User register form mode" which allows site builders to define a form mode at /admin/config/people/accounts that will be used for users without the permission 'Administer users' and potentially remove the default to use the Register form mode.
Remaining tasks
Confirm solution and implement
Original issue:
Atm, there's no way or UI so that one could assign the custom "form mode" to the User Register form.
Is that something already under the radar? I would like to work on this and contribute the same to core!