try many2one field for selection widget.

Two Ways for this:

1. First you can call a function in selection field to get the options for the field. Here is an example:

@api.model

    def get_field_options(self):

        #compute the list as per your requirement and for the list in format below

        value_list = [('one','option 1'),('two','option 2')]

        return value_list

dynamic_field = fields.Selection(selection='get_field_options', string="Field Dummy")

2. If you just need values from a table as a selection, then try many2one field with selection widget.

Hope this helps :)