I also made a fresh install with the version at https://ftp.freedombox.org/pub/freedombox/hardware/pioneer/nightly/: /etc/apt/sources.list refers to stable, but it is bookworm.
Then I immediately changed stable to bookworm. The additional file for the backports refers to bookworm, so perhaps the issue was that I was upgraded to trixie (because of stable) but keeping bookworm backports?
I am going to restore based on this new installation. I have left the option for auto-upgrade to next release ticked, and after last night upgrade, there is a notification that it will upgrade to trixie in 38 days. Looks like a good idea to have some delay like this.