The Trust Distribution tab of the Web Certificate page explains how to make client machines trust the Signotaur server's HTTPS certificate. It is shown only when the certificate's trust anchor (the Root CA certificate) is not already trusted; that is, when the server uses a self-signed certificate or a certificate from a private CA whose root is not in the client's trust store.

A card shows the certificate that must be installed on clients:
Download PEM and Download DER buttons provide the certificate in either format: PEM (.crt, Base64 text) or DER (.cer, binary).
An accordion provides step-by-step instructions for each platform:
update-ca-certificates (Debian/Ubuntu) or update-ca-trust (RHEL/Rocky/Fedora).After installing the certificate, fully close and reopen the browser (not just a tab reload) so it picks up the new trusted root. If a page was already loaded over the untrusted certificate, the browser may keep showing a warning for the rest of the session; open the site in a fresh window to confirm trust is working.
The Trust Distribution reference page covers the same trust-installation steps for every platform, including the case of a manually configured self-signed certificate rather than the managed CA.