I tried this: https://www.dell.com/support/kbdoc/pt-br/000131486/atualizar-o-bios-da-dell-em-um-ambiente-linux-ou-ubuntu on my Dell XPS 13 9310. I formatted the usb drive as FAT32 and copied the .exe file to it, but when I enter the bios update option it cannot find the usb drive. I tried many options, pressing F12 or F2 on boot, etc.
I also know that it can be updated through update manager, but I don't see a BIOS update in my software updater