Internet-Security.com TCP port 8448 details

TCP 8448 is the default port used by the Matrix protocol for server-to-server federation over HTTPS.
Matrix homeserver implementations such as Synapse, Dendrite, and Conduit commonly listen on 8448 for federation traffic.
The public matrix.org homeserver and many hosted Matrix providers (e.g., Element/Modular) expose 8448 to other homeservers for inter-server communication.
Many self-hosted Matrix deployments also publish 8448 externally (sometimes via a reverse proxy) to enable federation.
Some deployments may additionally serve client traffic on 8448, but its primary real-world use is Matrix federation.

TCP 8448