Kernel ABIs change quite often, which means that new linux-image-VERSION-ABI-amd64 packages get released which are co-installable.
We have some servers which have /boot on a separate partition, which may fill up (for most other servers it's just a bit of wasted space, but for small Ganeti VMs it can also be an issue).
We should automate the removal so that one kernel in addition to the currently running is preserved (for falling back) and unused ones are cleared. One case to consider is that some servers get rebooted less often, so there can be cases where e.g. -12- is running and -11-, -13- and -14- are installed, but unused. In this case the running kernel needs to be kept and -11- and -13- can be dropped.
With bullseye apt even does this automatically and for older apt releases we most probably grab the information from "apt-get autoremove". This should also initially be opt-in to testdrive on some systems first.