If you are trying to burn a CD or DVD, K3b should do the trick.
K3b>more actionss>burn image.
Just burning the ISO as data will not work, as the software has to extract the ISO before burning it to the CD\DVD.
If your are trying to write to a USB Drive, then I like Etcher myself. It is no longer in the official Ubuntu repository, but can be downloaded at :
You want the " balena-etcher-electron_1.5.109_amd64.deb " file and install with gdebi.
You will find it under "Accessories" after installation. Etcher is pretty self-explanatory to use. It will not update when installed this way, but will tell you when a new version is available.