Update beyond 2.21.02

Dear all,
I need help to update deCONZ beyond 2.21.02.

I have a ConBee II usb stick running headless on a raspberry pi 2 with Bullseye.

I’ve used the system for a couple of years and it has been working fine. I’ve followed the instructions on phoscon’s homepage, but apt update dosen’t seem to get me the latest stable version anymore.

Any thoughts or advice on this issue?

Thanks in advance and regards!