To resolve this, DSM allows you to manage certificates through Control Panel > Security > Certificate. You can request a free certificate from Let's Encrypt directly through DSM, provided the NAS is associated with a public domain name and is reachable via ports 80 and 443. This option is excellent for users hosting services or accessing their NAS remotely. Alternatively, users can import certificates from a trusted Certificate Authority (CA), which is often required in corporate environments. Once installed, the certificate can be assigned to DSM services to ensure browser trust.
www.techbetime.com/2025/02/dsm-71-setup-configuring-web-gui-to.html