A new beta boot loader (will be out of the beta pretty soon) has been released for the raspberry pi 4 which supports USB boot natively, without the need of an SD card. Are there any plans for supporting that feature on Ubuntu in the near future?
I can confirm that
Ubuntu 20.10 x64 (and I'm guessing
x32 as well) can be installed on an external SSD to be used natively with the Raspberry Pi 4. To write Ubuntu on an SSD, one should use the Raspberry Pi Imager from here.