Try adding a [%s] at the end. I needed this too for my Spotify binding to show the strings in the sitemap as you can see at “Titel” and “Künstler”
I do not think Frame widget supports linking to an item in this way. It might well have worked once as an undocumented feature.
Docs say it only supports label= and icon=
I see no reason why you couldn’t ask for Frame widget enhancement, perhaps to act like a Text widget when an item= is given.
But that affects all sitemap based UIs and OH core, so don’t hold your breath.
Currently Basic UI displays square brackets around the item value. They should be removed. If someone opens a GitHub issue and this behavior gets approved, I can fix it in the Android app.