For Linux you don’t need a GUI tool, most how tos just dd the ISO onto the USB medium, e.g.
sudo dd if=<file> of=<device> bs=16M status=progress oflag=sync
like described in the Debian FAQs
I don’t remember where, but i read that this method only works because linux distributors “abuse” the ISO format to allow this. If I remember right, it’s not possible to use this ISOs on regular disks
Of course the command you provided is right and it’s what I use, it’s just a fun fact
Yes and no, it’s the other way round. The ISOs often are hybrid images which you can burn onto a CD/DVD or dd onto a USB pen drive. Until approximately 10-15 years ago, if I remember correctly, the distributed Linux ISOs where standard not hybrid images, thus you always needed some other program to create bootable USB media.