It’s free for a limited number of personal devices. Add the jellyfin server to your tailscale network and it will receive a local ip. Add you grandfather’s roku (or possibly router) to that same tailscale. You’ll then be able to enter the Tailscale ip address of your jellyfin into the roku app to get access.
I don’t have a roku, but use tailscale to access several home services while I’m out including a jellyfin instance. It is incredibly easy to setup and use, particularly if you are limited by complex router situations.
Tailscale
It’s free for a limited number of personal devices. Add the jellyfin server to your tailscale network and it will receive a local ip. Add you grandfather’s roku (or possibly router) to that same tailscale. You’ll then be able to enter the Tailscale ip address of your jellyfin into the roku app to get access.
I don’t have a roku, but use tailscale to access several home services while I’m out including a jellyfin instance. It is incredibly easy to setup and use, particularly if you are limited by complex router situations.