If you only want to update your Ubuntu live disk with a new ISO image, then
just install the new image to the drive as you did earlier. No need to delete first.
If it's about formatting a drive that previously contained an Ubuntu ISO image, then you most likely have to remove the odd partitioning that these ISOs bring.
Use your partitioning program to ...
made using Rufus 3.8
Is it officially known to work? Rufus has been known to cripple hybrid ISOs for quite some time around me (like UltraISO or UNetBootin), so we ended up recommending plain dd or imagewriter-- maybe try writing ALT Rescue this way and if it works, you at least know the path :-)
Another source of trouble might be 32-bit UEFI firmware ...
Light-weight Ubuntu flavour
I suggest that you select an Ubuntu flaour with a lighter foot-print than standard Ubuntu, Lubuntu or Xubuntu version 18.04.3 LTS.
You can use mkusb in order to create the persistent live system automatically, if you have access to Linux.
If you run standard Ubuntu live, you need an extra instruction to get the ...