Pi4B and Pi5 have USB boot enabled by default and will "just work" with a correctly prepared USB boot device. (Early Pi4B may require a firmware update first).Last I saw, switching to boot from USB, whether using Pi Imager, or booting and then using raspi-config would require a microsd card (in either case) if only for that first boot. That said, as it seems it was used previously, there is a chance that the boot from USB was already enabled. Otherwise, a minimal sized microSD may be needed.
Zero 2W, later 2B, 3B and 3B+ need a line in config .txt run once from an SDCard to enable it.
A, B, A+, B+, and early 2B do not support USB boot.
See the documentation.
Statistics: Posted by davidcoton — Sat Jun 29, 2024 8:34 am