Expand the "Installation Instructions" part, and you'll see "Updating the BIOS from BIOS Boot Menu (independent of operating system)"
I don't know if Dell supports it across all their laptops, but it has on the ones I've owned.
Other Lenovo laptops have a recovery mode (Fn+R) where some bootstrapping firmware would flash a BIOS from USB, they neglected to include that feature in the (presumably lower cost) Flex lineup.
Some folks out of support went as far as desoldering the EPROM with the BIOS and hooking it up to a flash programmer, to get the laptop unbricked.
I realize they have a lot of different models and probably a limited test matrix, but it's still unforgivable to push a forced update that bricks the device to this level (and until that happened I didn't even know OEMs can push BIOS updates over Windows Update, probably because most of my machines are custom builds).
Why would that be hard? They're the manufacturer; all they have to do is keep a handful of every model they've made, stick them in a room connected to network and power, and have Jenkins run a job on them that flashes the firmware and reboots. I know I'm oversimplifying, but I don't think I'm oversimplifying by that much, and it shouldn't be hard for the manufacturer to keep test units of their own hardware on hand.
I bought a motherboard and a new AMD Zen 3 CPU together recently. The motherboard wouldn't POST because the BIOS was too old to and didn't have Zen 3 support.
The only way to get it to work was to flash a new BIOS using the out-of-band update tool that works with just the PSU and USB stick attached.
Without that you would need a spare CPU knocking about...
And I use my re-write of geteltorio to flash it on a USB drive: https://github.com/hspak/geteltorito-zig
I've done this multiple times now without issues, but your milage by vary!
It had been sitting in a cupboard for a good year or two and when powered on it produced no video output, or BIOS/POST screen. The backlight for the screen didn't even come on.
While it wasn't particularly easy to troubleshoot. I eventually managed to flash an uncorrupted version of the BIOS over USB and it's been working fine since.
It does not work on the Flex model line-up though (I presume because they didn't include the bootstrapper firmware or some h/w component).
Source for this? I've seen it available on various enthusiast desktop motherboards, but I haven't seen it on laptops. I haven't even seen it on the pricier thinkpad line.