Welcome to the forums, jcrowley17!
In my experience, the Fedora Media Writer works fine to create Ubuntu liveusb's.
First, download the .iso of the Ubuntu installer.
Second, follow the instructions in the following article (link below). Skip the step called "Creating a Fedora USB." When you get to the step called "Already have an ISO downloaded?" this is where you click Custom Image and choose the Ubuntu .iso that you downloaded in step 1.
https://fedoramagazine.org/make-fedora-usb-stick/