I think the same issue is tracked in Ubuntu Launchpad as https://bugs.launchpad.net/ubuntu/+source/plymouth/+bug/1592405. Unpacking linux-image-amd64 (5.9.15-1~bpo10+1) over (5.9.6-1~bpo10+1) ... Setting up linux-image-5.9.0-0.bpo.5-amd64 (5.9.15-1~bpo10+1) ... I: /vmlinuz is now a symlink to boot/vmlinuz-5.9.0-0.bpo.5-amd64 I: /initrd.img is now a symlink to boot/initrd.img-5.9.0-0.bpo.5-amd64 /etc/kernel/postinst.d/initramfs-tools: update-initramfs: Generating /boot/initrd.img-5.9.0-0.bpo.5-amd64 cp: cannot stat '/usr/share/fonts/truetype/ttf-dejavu/DejaVuSerif.ttf': No such file or directory E: /usr/share/initramfs-tools/hooks/plymouth failed with return 1. update-initramfs: failed for /boot/initrd.img-5.9.0-0.bpo.5-amd64 with 1. run-parts: /etc/kernel/postinst.d/initramfs-tools exited with return code 1 dpkg: error processing package linux-image-5.9.0-0.bpo.5-amd64 (--configure): installed linux-image-5.9.0-0.bpo.5-amd64 package post-installation script subprocess returned error exit status 1 dpkg: dependency problems prevent configuration of linux-image-amd64: linux-image-amd64 depends on linux-image-5.9.0-0.bpo.5-amd64 (= 5.9.15-1~bpo10+1); however: Package linux-image-5.9.0-0.bpo.5-amd64 is not configured yet. dpkg: error processing package linux-image-amd64 (--configure): dependency problems - leaving unconfigured Errors were encountered while processing: linux-image-5.9.0-0.bpo.5-amd64 linux-image-amd64
This still seems to be an issue, the script checks if the dejavu font is present and if it is not it continues, but then the call to build the fc-cache fails, presumably because no fonts are present in DESTDIR.