On iOS you can set a proxy right in the Wi-Fi settings. tvOS has no such setting — the only way is a configuration profile that sets the proxy and adds the root certificate to trusted ones. ProxyBeam generates that profile for you.
In {{ guideName }} on your Mac, choose {{ menuPath }} and save the certificate in the .cer format.
Open ProxyBeam and drag the saved .cer file into the window (or click Choose File…). The app starts a local server and shows a link like http://192.168.x.x:PORT/proxy.mobileconfig. Click the link — it's copied to your clipboard.
On the Apple TV, open Settings → General → Privacy & Security. Highlight Share Apple TV Analytics — but don't click it. Press Play/Pause on the remote — a profile menu opens. Enter the link from step 2 and press Play/Pause to confirm.
Go to Settings → General → About → Certificate Trust and enable trust for {{ certName }}.
{{ guideName }} must be running on the Mac and listening for connections — the default port is {{ port }}. The Mac and the Apple TV must be on the same Wi-Fi network.