You can call on unetbootin. It's discussed here, viewtopic.php?p=6801#p6801. Just follow the links. Using it under Puppy (Bionicpup64 to be specific) revealed a couple of thing regarding the unetbootin.bin downloaded.
(1) I kind-a recalled Unetbootin didn't provide a routine for formatting the USB-Key. So, before plugging it in, gparted formatted it as fat32. Running it also didn't suggest any opportunity to format.
(2) That Unetbootin also required the USB-Key be mounted came as a surprise.
(3) mtools was a simple one-deb download via PPM. Installed and x-restarted. Until mtools was installed Unetbootin could not see the USB port.
(4) The ISO selection routine didn't work. Only the files/folders in /root were listed and there appeared to be no way to 'escape' from there. So I created a 'secret passage'
--a symlink to the folder where the ISO I wanted to use was located. I guess I should have anticipated this. Most distros think that a 'User's place is in his/her Home'. And they don't want you rooting-around. Now, with my secret passage I can sneak out of my Home and cat-around without puritanical Unetbootin being anyway the wiser. 
My first 'conquest': LinuxMint 20.
