I also used to bring a chromecast to connect to hotel TVs, but no longer do. When I stay in a hotel and I see that the TV has a chromecast hooked up to it (or baked into it or whatever), I don't bother even trying to connect to it anymore. The DIAL protocol only allows service discovery on the local network, and in my experience local networks are more or less never configured correctly for it.
The several times I've tried connecting, when the phone fails to discover the TV automatically, the TV offers some kind of pairing code that I can type into the google home app (on ios). Before learning more about DIAL, I had thought that this would enable my phone and TV to connect through some google-managed proxy in the cloud, for just such cases where both the phone and TV can make outgoing connections, but can't open connections to each other for whatever reason.
I can't imagine why there isn't a fallback built into DIAL that lets me scan a QR code on the phone (or have the TV play some audio that the device decodes, if the mobile device doesn't have a camera or for a11y purposes, or whatever) and have both devices communicate through a proxy. Such a proxy would be extremely low bandwidth and would be latency-insensitive, so really really cheap to run. DIAL is predicated on both devices being able to access media URLs, so I think this fallback would only fail in a case where the TV/chromecast can't connect to the internet and is being used to display content from the LAN. This latter case is probably very niche compared to people not being able to connect their devices because of routing issues.
I also used to bring a chromecast to connect to hotel TVs, but no longer do. When I stay in a hotel and I see that the TV has a chromecast hooked up to it (or baked into it or whatever), I don't bother even trying to connect to it anymore. The DIAL protocol only allows service discovery on the local network, and in my experience local networks are more or less never configured correctly for it.
The several times I've tried connecting, when the phone fails to discover the TV automatically, the TV offers some kind of pairing code that I can type into the google home app (on ios). Before learning more about DIAL, I had thought that this would enable my phone and TV to connect through some google-managed proxy in the cloud, for just such cases where both the phone and TV can make outgoing connections, but can't open connections to each other for whatever reason.
I can't imagine why there isn't a fallback built into DIAL that lets me scan a QR code on the phone (or have the TV play some audio that the device decodes, if the mobile device doesn't have a camera or for a11y purposes, or whatever) and have both devices communicate through a proxy. Such a proxy would be extremely low bandwidth and would be latency-insensitive, so really really cheap to run. DIAL is predicated on both devices being able to access media URLs, so I think this fallback would only fail in a case where the TV/chromecast can't connect to the internet and is being used to display content from the LAN. This latter case is probably very niche compared to people not being able to connect their devices because of routing issues.