Xpra itself ships this script, but Debian’s version is quite old. You need at least 4.1 and Debian Bookworm seems to have 3.1. Xpra seems to have an own apt rep

Xpra itself ships this script, but Debian’s version is quite old. You need at least 4.1 and Debian Bookworm seems to have 3.1. Xpra seems to have an own apt repo you can probably use.