Although most Raspberry Pi users choose Raspbian as their operating system, the fact is that this mini quasi-system can run many GNU/Linux releases, including Ubuntu. The problem with installing the Ubuntu system mirror, however, is the presence of Linux kernel BUGS in Ubuntu 19.10, which prevents the 4GB of Raspberry Pi 4 from using the USB port.
There is currently a temporary workaround for this bug, which enables USB on 4GB Raspberry Pi 4, which involves editing/boot/firmware/usercfg.txt files, limiting memory to 3GB instead of 4GB by adding the “total_mem s 3072” line (without quotation marks). Canonical is currently working on a kernel patch for the vulnerability, which will soon be released to everyone.
Despite the temporary solution, Canonical finally fixed the vulnerability today, introducing 32-bit and 64-bit mirrors for The Raspberry Pi 2/3/4. Galem KAYO, project manager at Ubuntu Core at Canonical
In the new image, the USB port is also fully available on the 4GB memory Raspberry Pi 4. This kernel BUG limits the Ubuntu system to support only 1GB and 2GB of motherboards. The BUG has now been fixed and this restriction has been lifted.
Canonical promises comprehensive ready-to-use official support for its Ubuntu Linux operating system on all Raspberry Pi singleboards, including the original Raspberry Pi single board and all Raspberry Pi 2, Raspberry Pi 3 and Raspberry Pi 4 models. Raspberry Pi will officially support Ubuntu Server and Ubuntu Core.
Canonical wants the Ubuntu Linux operating system to be a more attractive option for The Raspberry Pi, so it needs community support. Canonical currently offers Abuntu 19.10 and Ubuntu 18.04 LTS versions for Raspberry Pi, both of which support Raspberry Pi.