I know I'm supposed to have the Startup Disk Creator installed in the Ubuntu 19.04 version, but I ran the
apt policy usb-creator-gtk
And got
usb-creator-gtk:
Installed: (none)
Candidate: 0.3.5
Version table:
0.3.5 500
500 http://se.archive.ubuntu.com/ubuntu disco/main amd64 Packages
What I want to do is boot my other PC with a USB stick, I've already installed the Ubuntu 19.04 on the USB stick, but the PC is not detecting it (it is not in FAT16 format, and I can't figure out how to reformat it).