follow this way:

1. Create a new Python controller:

from odoo import http
from odoo.http import request
import os


class FileDownloadController(http.Controller):
 
    @http.route('/file/download', type='http', auth='user')
    def file_download(self):
        file_path = '/static/files/your_file.txt'  # Update with the actual file path
 
        # Get the absolute path of the file
        full_path = os.path.join(request.env['ir.config_parameter'].get_param('web.base.url'), file_path)
 
        # Read the file and return it as a response
        with open(full_path, 'rb') as file:
            file_data = file.read()
 
        # Set the response headers for file download
        response = request.make_response(file_data)
        response.headers['Content-Disposition'] = 'attachment; filename="your_file.txt"'  # Update with the desired file name
        response.mimetype = 'application/octet-stream'
 
        return response

1. Create a menu action that triggers the file download:

    field name="name">Download File/field>
    field name="type">ir.actions.server/field>
    field name="model_id" ref="model_your_model"/>
    field name="state">code/field>
    field name="code">
        action = self.env["ir.actions.act_url"].sudo().with_context(
            action_id=self.id, dialog=True).create({
                "name": "File Download",
                "url": "/file/download",
                "target": "new",
            })
        return {"action": action}
    /field>
/record>

1. Add the menu action to the desired menu:

menuitem id="menu_item_file_download" name="Download File" action="menu_action_file_download"/>

With this setup, when the user selects the "Download File" menu item, the file will be downloaded through the custom controller's file_download method.


note: here i remove the XML tag like(< >) because when i edit the tag and save the answer the i didn't see the full code of XML,so please add the (<>) once you edit the XML file