Hello,
There are multiple options for achieving this, but the most viable ones include having a static IP for your router (usually obtained from your internet provider for a cost) or using a VPN. However, most VPNs require the server end to have a static IP, although some exceptions like Zerotier and Tailscale do not require this. On the rut240, only Zerotier is viable as it does not support Tailscale.
Additionally, you could acquire an app-controlled camera, eliminating the need for any other configuration. This would be the easiest and most beginner-friendly option.
Best regards,