K3s agents and servers maintain websocket tunnels between nodes that are used to encapsulate bidirectional communication between the control-plane (apiserver)
Edit /etc/rancher/k3s/config.yaml and add egress-selector-mode: disabled to disable the tunnel encapsulation, then you can redirect the flow to cloudcore.
Alternative: create override conf for systemd unit
Create /etc/systemd/system/k3s.service.d/override.conf
[Service]
ExecStart=
ExecStart=/usr/local/bin/k3s server --egress-selector-mode=disabled
reload conf and restart:
sudo systemctl daemon-reload
sudo systemctl restart k3s