Windows browsers such Firefox, Chrome, Vivaldi, Brave have the same issue. It’s not OS or device related, it’s how Chromecast has been implemented in Jellyfin.

https://github.com/jellyfin/jellyfin/issues/6840#issuecomment-1042905147

I’m also the developer of a local media server, and I’ve easily managed to bypass the Chromecast client-side issues by doing a server-side discovery. Now no matter how I access my media content, I can always send it to a Chromecast, because the CC and my server are on the same network, so the CC can easily be discovered over Avahi/Bonjour/mDNS. Then it can be the server itself to provide the client with a list of discovered players, not necessarily the other way around.
The fact that there’s no server-side logic to manage the Chromecasts, and instead we rely on the client to discover them, explains why things are so broken. Why not provide a server-side CC scan logic as a backup for users who don’t use Chrome on Android but run the server on the same network as the CC, instead of relying on such a brittle client-side implementation?

This is why! It’s a crappy implication…

https://github.com/jellyfin/jellyfin/issues/6840#issuecomment-1042905147

iPhone has no Play Store. I got the app from the AppStore for iPhone, no luck, chromecast does not work.

Yup… I have a reverse proxy. Chromecast in Emby works, Chromecast in JellyFin doesn’t. Really weird.

Chromecast in JF never worked…
When I click the chromecast icon in JF “Play On” (top right) I get “Google Cast Unsupported”.

How did you manage to get it working?

JF has no proper chromecast support… ☹️😤