Hello ilias,

its base User Error for restricting company duplication.
Still you want to fix this then you have to override base copy method and handle the same.

​import logging
from odoo import api, fields, models, tools, _, Command


class Company(models.Model):
    _inherit = "res.company"

	​def copy(self, default=None):
	​	_logger.warning("Duplicating a company forcefully")​
    	​#raise UserError(_('Duplicating a company is not allowed. Please create a new company 	​	​	​#instead.'))