Bug#1000621: /etc/ssh/sshd_config options: ClientAliveInterval and ClientAliveCountMax not working

Package: openssh-server
Version: 1:8.4p1-5
OS: Debian 11 (Bullseye)

Hello,

configuration ClientAliveInterval and ClientAliveCountMax do not disconnect
idle ssh sessions.
The Previous openssh-server package (1:7.9p1-10+deb10u2) used in Debian 10
worked fine.
For example configuration in /etc/ssh/sshd _config
*ClientAliveInterval 15*
*ClientAliveCountMax 0*
It disconnected the idle ssh session after 15 second, unfortunately this
configuration is not working on Bullseye with the stable (1:8.4p1-5) or
testing version (1:8.7p1-2).

Kind regards
Martin Jungmann