Non-existent media player entity shows up everywhere

Hey there,
All my devices discover a media player entity which can’t be found in my Home Assistant configuration anymore. I looked up under integrations and entities but it doesn’t show up anymore. I want to get rid of it, because it shows up as a FireTV/Chromecast option everwhere.
I’m 100% sure it’s Home Assistant because Alexa let me see the entity name: “media_player.arbeitszimmer via Home Assistant” but it’s not anywhere to be found. Any idea?