When they released the Ubuntu 19.10 (Eoan Ermine) operating system series last month, Canonical said that Raspberry Pi’s Foundation’s latest Raspberry Pi 4 boards will be officiallly supported. However, Ubuntu 19.10 ships with a Linux kernel bug that blocks the use of USB ports out of the box in the official arm64 image on the Raspberry Pi 4 SBC with 4GB RAM. There’s a temporary workaround to enable USB on Raspberry Pi 4 boards with 4GB RAM, which involves editing the /boot/firmware/usercfg.txt file to limit the RAM to 3GB instead of 4GB by adding the “total_mem=3072” line (without quotes). Canonical is currently working hard to test kernel patches for this bug, which should soon be released for everyone.