Home Assistant Tags

Ok, you found the device id of the tag reader in developer tools. It can be found also in the /config/.storage/core.device_registry file and there search for “tagreader” (or whateven you named the tagreader) and see the “id” field.

The speaker choice in the Spotify environment (selection of the “source”) is a different problem, as Spotify treats that as dynamic items and HA uses the Spotify API and so cannot do much about it. See the long discussions here.
A sort of solution can be found in the HA custom component Spotcast but I have no experience there.

My Spotify default “Source” is (perhaps by accident :wink: ok, but this is the part where I’m also still wrestling as I want to use two more (media) tagreaders in the house.