Maybe these help:
https://forum.proxmox.com/threads/unable-to-upgrade-to-new-kernel-no-space-left-on-device-but-df-says-otherwise.108994
https://forum.proxmox.com/threads/dpkg-hanging-when-upgrading-pve-kernel.95077...
Thank you Neobin, this was the procedure I used...
cat /etc/kernel/proxmox-boot-uuids
67D6-E50C
ls -al /dev/disk/by-uuid/67D6-E50C
lrwxrwxrwx 1 root root 15 Sep 1 20:06 /dev/disk/by-uuid/67D6-E50C -> ../../nvme0n1p2
mkdir /tmp/myesp
mount...