Comment 4 for bug 1901395

this is exactly the issue during an upgrade of a pine64+. the boot partition was created at 100MB so it is quite impossible to go to 100MB

there is not much there:

 du -sch /boot/*
2.0K /boot/Image.version
3.4M /boot/bat
10K /boot/boot.cmd
10K /boot/boot.scr
3.1M /boot/bootlogo.bmp
338K /boot/font24.sft
350K /boot/font32.sft
1.1M /boot/initrd.img
11M /boot/kernel
4.4M /boot/pine64
2.0K /boot/uEnv.txt
2.0K /boot/uEnv.txt.in
23M total

but there must be a solution to having too small a partition, and if there is not, then an image for pine64+ would be appreciated