I installed debian for a friend who is not techy. They've been accepting the updates as and when offered. Now their /boot is full. I'm assuming they need to run

apt autoremove --purge

Or similar. But is there a way you automate this? Otherwise debian with a boot partition seems to have a self destruct timer!

Advice appreciated!

Would rec moving them to something more simple, akin to ElementaryOS.

That said, /boot likely isn’t right sized for the number of versions of the kernel required by the bootloader in case of a failure. 512mb-1gb of storage is normally more than enough to handle said copies. As well, apt dist-upgrade will actually remove obsolete packages while apt upgrade does not.

This is one of the reasons why I don't use a separate partition for /boot anymore. As I understand it, a separate /boot partition is mostly a legacy thing unless you have an encrypted root partition or some other special setup. For simple cases I recommend having /boot on the root partition to avoid issues like this.

I think that's also the default setup used by the Debian installer if you select Guided partitioning – use entire disk. I'm not 100% sure tho.

apt full-upgrade takes care of this

They're using the automated updates. I guess that's not doing the apt full-upgrade or dist-upgrade ...

I allocated 1GB for boot. I'm using separate boot to have encrypted root.

Full and dist are two separate actions. I would highly recommend you pop the man page for apt.