So, having had my interest piqued, in another forum thread I gave it a go....
Yes it works!
First, dd a RaspiOS image to the drive, before restarting, go to /usr/lib/raspi-config/init_resize & change the line starting with
to something that will prevent it using up all the disk, these are in 'sectors', (& I think RaspiOS is using 4096 as the size).
I just stuck in TARGET_END=$((8000)), which prevented it from grabbing all the disk.
I then ran RaspiOS to check it was working OK, it was using about 3.3GB.
Shutdown RaspiOS, then install Linux to the rest of the disk as normal, I used AntiX, (my regular distro), & let it install grub to the MBR.
The RPi that I was using just booted up normally from my USB pendrive, & when I inserted into a regular computer, grub booted up Linux, no problem.
Edit: I was using RaspiOS64 on my RPi3B+
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