The screen and keyboard are invaluable for backups. I have a portable SSD with Ubuntu installed for creating backups, but I often have to manually set the boot device on startup to get it to work. Setting a USB SSD for the first boot device in the BIOS/UEFI doesn’t seem to work reliably on any of my systems.
I’ve found it to be simpler. Booting off a USB SSD allows full disk cloning to that same SSD without worrying about mounted partitions or using a separate USB thumb drive for Clonezilla. Once booted I can access the machine through SSH or NoMachine to create the backup and it is far faster than backing up to a network drive. For incremental backups Timeshift works fine.