Recently I got around to playing with an Amstrad PPC I'd had for a while but not tried to get running. I even had the thin version of the manual, ruck sack, power supply and half the system disks.
The good news is - it's easy ! I'm not even a hardware guy :)
Get a Gotek or OpenFlops drive - this provides the hardware interface between the PPC's floppy cable and the modern world of USB sticks for mass storage.
I wanted my Gotek as A:, and the original drive as B: - and my PPC already had a floppy cable with two plugs on, and no twists.
In theory this means I can copy to/from real physical 720k disks. If you do this, the original drive will still power on and spin on drive access, even to the Gotek. You might want to unplug it's power or fit a power switch if this bothers you. Or leave it out. You probably have a blanking plate anyway...
You can find out about the cable twist, and start the process of adding the drive, by undoing the two screws on the top to the right of screen, then sliding the section away from you, then up; careful as there are wires attached.
You'll then need to remove a ground wire and screw from the bottom of the trench.
The metal carrier for the drive bay slides to the left, then pull up the left side. Mine was very tight with cables. If you try and lift it straight up, it'll catch on the case, and that might be bad, but I got away with it once.
Once at an angle so it clears the top of the case on the left, pull the tray out at that angle, careful again with the cables
The correct jumper settings for me were to set the Gotek to SO and the original Amstrad drive to D1. My understanding is that if you have a duel header cable with a twist, the B: drive should be jumpered to D0 as well and the cable twist does the job instead.
Here's what that looked like shortly before bench testing prior to full reassembly. Jumpers are marked in red.
For bonus points, and because I used the wonderful folks at Retro32 (.com - but based in the UK like me), you can easily attach a small screen to the Gotek, to replace the three digit display. This helps because it shows the disk image name, not just the index number.
Retro32 took care of finding a Gotek, and flashing FlashFloppy to it, and getting a screen attached. You also get an Amiga mount 3D printed, so ask them to not toss away the Gotek case itself and just send you everything.
Total cost was waaay less what it would cost me to find the two hardware bits, and get a special flashing cable, fight with the flashing tools etc.
You wouldn't want to move the Gotek back and forth between machines very often, but it's all screws and push connectors so it'll do for me.
With the Gotek back in it's original housing, and a disk image from Archive.org copied to the USB stick (which can be otherwise empty, no need for any .CFG files), it all Just Works.
There are a few more photos at https://rachaelandtom.info/photos/index/category/921-amstrad_ppc_640 including a shot of the keyboard that shows where the tabs are (I had a sticky space bar I cleared up at the same time).
I've added ten C-cell batteries since, at a pound each(!), so ignore the errors you see about the date and time :)
Sadly it looks like the machine is just a little too old to pull the same trick with IDE or SCSI, so I won't be able to add a hard drive... at least without doing something cleaver like Interlink serial to USB to DosBox...
The right idea might be a (<720k) bootstrap .img on the Gotek, that just fires up Interlink(.exe) (DOS 6.22 ?) over serial. The other end can be anything from a Pi to a desktop machine running DosBox and the Intersvr.exe. The Amstrad side now has a C: drive image and/or access to mounted drives in the servers Dosbox.
OR if can cram into the 720k image, setup http://ftp.oldskool.org/pub/tvdog/internet/dosppp06.txt to a host server running PPPd, then http://www.brutman.com/mTCP/mTCP.html gets at least telnet...
Might also be fun to get GBS-8200 based CVA-to-VGA box and hook it up to a color monitor...