Go to the Odoo Apps menu and search for Lock Chatter Attachments. You will find the application as shown in the image below. Install the module to enable attachment locking and deletion restrictions in the chatter. Once installed, configuration options will be available in the Settings menu.

Go to Settings → Users and open any user form view. In the Access Rights or Other section at the bottom, enable the Manage Locked Attachments checkbox. Once this permission is enabled, the configuration section for locking chatter attachments will become visible in the General Settings.

After enabling the Manage Locked Attachments checkbox on the user form, go to Settings → General Settings. The Lock Chatter Attachments configuration section will now be visible. From here, you can select the models for which chatter attachments should be locked and protected from deletion.

Click on Configure Locked Models to open the list view for locked attachment configurations. From here, click the New button to create a new record. Enter a configuration name and select the model for which chatter attachment deletion should be prevented. Save the record to apply attachment locking for the selected model.

Open a record of a configured model, such as Sales Order. In the chatter, click on Attachments and attempt to remove an attachment using the Remove button. If the model is configured for locking, the attachment deletion will be restricted and the file will remain protected.

When attempting to delete a chatter attachment from a configured model, a validation message is displayed indicating that deletion is not allowed. This happens because attachments for the Sales Order model have been locked through the Lock Chatter Attachments configuration, ensuring protected files cannot be removed.