Is this why Home Assistant on my Raspberry Pi cannot install the Matter server update from 8.1.0 to 8.1.1 that it is telling me is available?

It gives this error:

> Error during service call to update.install: Error updating Matter Server: Can't install homeassistant/aarch64-addon-matter-server:8.1.1: 401 Client Error for http+docker://localhost/v1.51/images/create?tag=8.1.1&fromImage=homeassistant%2Faarch64-addon-matter-server&platform=linux%2Farm64: Unauthorized ("unauthorized: authentication required")

From the "localhost" in the URL I assumed it was an error with a local Docker instance but I have no idea how HA actually works under the hood. I used the install method where you use the Raspberry Pi Imager to make a bootable HA RPi image and that takes complete control of the RPi. There's a Linux in there, but I've got no login on it. It is a complete black box to me with all my interaction through their web interface or the mobile app. Presumably it has to get 8.1.1 of the Matter server from somewhere, and if that is failing maybe it makes the localhost Docker fail too?

Yes, that's an http connection to the Docker Engine api on localhost failing due to the same issue—the docker engine cam't negotiate with the Docker Hub to get the new image and is passing the error back through the local api to your updater process.