byobu-select-session does not select session, launches bare-bones screen session on Debian Bullseye

[Jon Brase]

I have two machines, one is running Ubuntu 20.04, the other Debian Bullseye. On each machine, I use zsh as my login shell, ~/.byobu/backend contains "BYOBU_BACKEND=screen", and my .zprofile contains:

[[ -o interactive ]] && byobu-select-session && exit 0

On the Debian machine, this line has been commented out for the moment due to this bug.

On the Ubuntu machine, this works as expected: on a console or ssh login, byobu-select-session is run, I get presented with the option to start a new session, select a running session, or launch a new shell, and byobu launches (unless a bare shell is selected) with the selected session and a configuration matching the contents of the ~/.byobu/ directory.

On the Debian machine, byobu-select-session behaves exactly as if "screen" had been invoked: no session selection is offered, and the screen session that launches has no byobu status line, does not respond to byobu keybindings, and otherwise behaves exactly like vanilla screen. I do not use tmux enough to be certain, but the behavior if ~/.byobu/backend is edited to select tmux appears to be the same: the tmux session that is launched appears to be completely vanilla with no byobu configuration loaded. The behavior is the same whether byobu-select-session is run through .zprofile or manually, and regardless of how the shell invoking byobu-select-session was started (ssh, console, terminal emulator in local X session).

Bare "byobu" launches a screen session with correct byobu configuration on both machines.