By soldering to the flex-pc, I mean to the tabs at the end of the ribbon cable. Simply tale a little steel wool or 400 grit sand paper to remove any oxides at the end, then use a generous amount of flux when soldering.
I’m referring to this sort of cable. It’s a PCB made from from flexible material, hence the name “Flex-PC”.
I had a Raspberry PI camera project not too long ago where I used something like this and soldered directly to the pads at the end of the cable, it wasn’t pretty but it worked:
Surely that will likely work… for a while that is, until the constant vibration of the printer breaks the solder connections. Remember, soldering wire to solder pads is not considered good practice to begin with, it’s hack but it can be done effectively.
You could provide additional security for the cable and its wires via hot glue which although I hate, this is the one use-case in electronics where it is justified. A better alternative is to use a electronic grade RTV silicone which is designed for this but there we go, another $10. I would stay away from electrical tape by all means, that ■■■■ should be banned in electronics, leave it to the electricians.
By jumper wires, are you referring to solid core wire like 24AWG? If so, I might recommend stranded silicone encased wire as it will be more shock and vibration resilient due to its flexibility and lets be candid, this board will see a lot of shock and vibe just because it’s in a printer. Here’s a link for some 30AWG wire I’ve used with good success that is also good for this purpose, it’s very flexible almost too flexible but I was using it to build a custom 3D mouse and needed something that would flex inside of the conduit. You can braid it to increase its strength and make it less clumsy to deal with.
Or you can just purchase it as ribbon cable which will make your job easier but there’s another $10-$30… ka-ching!!! This can be an expensive hobby indeed, one $10 purchase at a time. Make sure you select “Stranded” not “Solid” core. It’s not easy to find, trust me.
https://www.amazon.com/s?k=silicone+ribbon+cable
This one you can cheat on a bit. The best method to verify that is to use a multimeter and test continuity for the 9th pin to ground or the sheet metal shroud. This will confirm the function of the tin shroud. But yes, you should be able to ignore it.