Hi,
No there’s no way u can change it to radio/checkbox becouse it’s hardcoded in render function that type is select.
Aldought u could apply filters to settings when generating select field but it’s to difficould to track specific field ( for ex. if you don’t know key or prefix ).
If u want u can try with these filter:
acf/get_valid_field/type=select to find some specific key wich is only in users field and change type to checkbox or radio
