Is PCIE x4 bootable for NVMe SSD under Linux

[dukla2000]

Have you setup the eMMC to be bootable ?
Did you flash the image for RockPro64 (or Rock64) ? ..... (Don't fret, just asking.)

Yeah there are no issues with the eMMC itself. It has the 0.7.9 RockPro64 image on it and boots 4.4.132 kernel just fine, either on its own or with rootfs on the NVMe. Or indeed can boot 0.7.9 with 4.4.132 kernel from SDcard and still see the eMMC if I want (playing with the jumper during boot).

The issue is if I try boot a 4.18.0-rc8 kernel (inside 0.7.9) then the boot hangs as it cannot initialise the eMMC: this is a problem whether using an SDcard or the eMMC itself as the boot device.

Thanks for other pointers on serial console etc.