@nyanotech @gsuberland #NVMe is #PCIe which will require a whole PCIe toot complex, which is much more expensive and electrically demanding than SATA and espechally USB 2.0.
Personally, booting from USB is the most important feature for the @Raspberry_Pi #Pi3B+ & #Pi3A+ and up - including #CM3+ [lite] and #CM4 [S][lite]...
@nyanotech @gsuberland @Raspberry_Pi I mean the #CM4 does support #NVMe and there are even boards from #WaveShare that basically breakout all the ports of a CM4 in the Foodprint of a #Pi4B - including #PCIe in the Form of an M.2 2280 M-Key slot [with a single lane]...
Still, out of cost reasons, USB-Boot would've been the most versatile option allowing anything from a cheap & slow USB 2.0 Thumbdrive [or even 3,5" FDD if supported for retro fans] up to a huge-ass array of HDDs and/or SSDs...