remove the automatic default role

but the default role assign prevents variants of this form from working well

Which form?

– Are you using a plugin for this feature? Yes? What’s the full name of this plugin? Where did you download it from?
– Is this a feature of your active theme? Yes? What’s the full name of this theme? Where did you download it from?

https://make.wordpress.org/support/handbook/forum-welcome/#include-as-much-information-as-possible