If you just want to communicate with it in your local network, it is possible by default and needs no TLS certificate as long as you trust all devices on your local network. I think exposing the Umbrel node to clearnet is also possible, but you maybe have to change your router config (open up ports)
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But a way better solution for remote connecting is to connect to your home with a VPN and then browse your Umbrel like your on the local network
