Linking to the systemd specification doesn't support the position that it's common to use systemd partition discovery INSTEAD of fstab. Are you aware of any major Linux distros that prohibit the use of fstab?
I installed the image to USB drive and it still didn't work. I'm just going to install a standard Linux distro and try to install Channels on top. The RPi image is probably too limiting anyway.
Not that prohibit the fstab, but if you were aware of how systemd works, fstab is used as an input, and the system creates native mount unit types.
All of this a bit irrelevant, though. The RPi image for Channels is meant to be used as a simple appliance type install, where you image it to an external USB drive to handle everything all-in-one.
If you want more control over your system, such as multiple drives, or the ability to host other software beyond Channels, then install a classic Linux distro and install Channels in the normal way.
No, this doesn't address the original issue, as the drive should be recognized. However, running from an SD card and having the primary storage on a separate drive is not how the system was designed, and isn't really a supported installation of the Pi image.