They should still be possible. It’s not clearing the BIOS though, it is clearing variables loaded into the BIOS. The OS needs to be able to write to them. A good one limits what an OS can write or rebuilds them, a bad one bricks.
thank you! I think this is what needed to explore
It is not my level to edit these things, I'm just Linux newbie exploring the possibilities.
But I still can't wrap my head over dd not being able to wipe a storage device out, despite being described as a "low level tool that can write zeroes to targets" in the discussion I viewed online.
You can mount the efi partition, but I don't think you can usually mount the uefi or bios. I've only ever edited vbios, and haven't done so in quite some time, but I remember needing to clamp the vbios chip. Dunno if motherboards make their bios chips more accessible, but I kinda doubt it.
Some motherboard support starting bios/uefi updates from a booted OS, so there might be a vector to be found there.
Early true BIOSen were stored on EPROM, which couldn't be rewritten while on the board, so those were read-only.
Later BIOSen were often on EEPROM or other chips that could be reflashed while on the board. According to Wikipedia, that started in the mid-1990s. However, you usually needed physical access and/or special software tools to do an overwrite—you couldn't mount these as a filesystem.
UEFI is quite different from legacy BIOSen and can be mounted as a filesystem, but how much it can be tampered with varies between implementations and devices.
So you would have been correct up until about 30 years ago, but not for modern systems.