Bionic = Ubuntu Bionic 18.04 (LTS) > old-stable?
Disco = Ubuntu Disco 19.04, no end-user support > remove
Focal = Ubuntu Focal 20.04, no end-user support > supported?
Archives can be uncompressed with 7-Zip on Windows, Keka on OS X and 7z on Linux (apt-get install p7zip-full). RAW images can be written with Etcher (all OS). > recommend USBimager instead of Etcher or link to the matching documentation page