in this generation: xps 9350: https://secure-lvfs.rhcloud.com/lvfs/device/33773727-8ee7-4d81-9fa0-57e8d889e1fa precision 5510: https://secure-lvfs.rhcloud.com/lvfs/device/124c207d-5db8-4d95-bd31-34fd971b34f9
Otherwise put the .EXE from support.dell.com on a FAT32 USB key or on the ESP and select flash BIOS from the F12 POST menu.
Re: EFI updates
xps 9350: https://secure-lvfs.rhcloud.com/lvfs/device/33773727-8ee7-4d81-9fa0-57e8d889e1fa
precision 5510: https://secure-lvfs.rhcloud.com/lvfs/device/124c207d-5db8-4d95-bd31-34fd971b34f9
Otherwise put the .EXE from support.dell.com on a FAT32 USB key or on the ESP and select flash BIOS from the F12 POST menu.