Comment 3 for bug 1937924

I'm unable to replicate the issue of a typical apt upgrade to the linux-raspi -1015 kernel on hirsute server breaking boot, with either SD card storage or a USB as the root device.

Copying things between boot partitions can be done as a temporary fix for things, but ultimately (as discussed on IRC), you want to use "sudo flash-kernel" after a successful boot to ensure that the kernel & initrd on the boot partition match whatever's on the root (including modules etc).

On the Xubuntu desktop question: how exactly did you set up the Xubuntu desktop? There's no official release of Xubuntu for the Pi, so I'm guessing this was either an Ubuntu server or a desktop image onto which the xubuntu-desktop package was installed?