Hi,

Please refer to the code:

from odoo import api, fields, models

class ProductTemplate(models.Model):
    _inherit = "product.template"

    allowed_branch_ids = fields.Many2many(
        'res.branch',
        string="Allowed Branches",
        compute="_compute_allowed_branch_ids",
    )
    branch_ids = fields.Many2many(
        'res.branch',
        string='Branch',
        domain="[('id', 'in', rec.allowed_branch_ids.ids)]",
        help="Branches associated with this product template"
    )


    @api.depends('categ_id')
    def _compute_allowed_branch_ids(self):
        """Compute allowed branches from category"""
        for rec in self:
            if rec.categ_id:
                rec.allowed_branch_ids = rec.categ_id.branch_ids
            else:
                rec.allowed_branch_ids = [(5, 0, 0)]  # clear

Hope it helps.