Linux Hint published a tutorial about how to boot the Raspberry Pi 4 from USB SSD.
How to Boot Raspberry Pi 4 from USB SSD?
Learn how to boot your Raspberry Pi 4 from a USB SSD. As well as experience its several benefits. To mention some, it has cheaper storage, faster boot time, and a longer lifespan than a microSD card. Check out this article to know more and the things you will need.
How to Boot Raspberry Pi 4 from USB SSD? – Linux Hint