Hi all, after a long process of trial and error I've gotten my fuji x-t1 to work and can use it for imaging, but it seems that the maximum shutter time I can use is 30 seconds (it seems the longer times of 1m+ available on the x-t2 onwards weren't included for the x-t1 unfortunately), so I've been thinking a good way to address my problem was to go down the route of an external shutter release. Not only would it give me more flexibility in shutter times, but I'd be able to shoot longer than 30s finally. However, there doesn't seem to be a whole lot of information regarding what exactly the specifications of this cable should be. I've seen guides on how to DIY one using a serial cable and some other components, but for something so simple in concept on the surface it seems a bit excessive. There do seem to exist USB to 2.5mm audio jack cables, and to my uninformed perspective it sounds like those should do just fine, but I have a suspicion the DIY cable is more complex for a reason. So this is all to say, what sorts of requirements would this shutter release have to satisfy in order to work/how would I tell if a given cable would work?. If anyone could point me to some extra information it would be greatly appreciated!

You're right: those serial cable components are vital. A remote trigger is nothing more complex than "closing a switch" (in fact you can do it with your finger tip ), something than a standard PC is "electronically" not capable of, at least without a dedicated circuit. In particular, USB signals are totally different animals.
DIY guys use a pre-made USB-to-serial cable (that's not simply "a cable", since it contains a small circuit inside itself) to obtain a simple "on/off" signal at one of the serial "pins", that can be driven through some software instruction; then add the necessary circuit (the components you said) to let it become a "switch". Eventually it becomes a "software controlled switch", that's exactly what's needed for a shutter release command.
Luckily, those additional circuits are very simple, and can be realized without a PCB, needing only some soldering skills.
Lacking the skills, I understand that could be scary, but not impossible.
Otherwise, you could find someone near you that's able to help you building it.

Sorry to carry the bad news, but hope to have helped you clarify things a bit.

Thank you so much, this really helps! I already have experience soldering and building circuits, so this shouldn't be a problem. It looks like I now have a small project to look forward to on the weekend!