USB host is unfortunately more than just a cable . It's a use case ;a protocal involving hardware , software and/or firmware . Now I have no idea what kind of hardware is inside the beatstep pro , but I imagine the chip(s) are quite busy doing cv to midi , midi to cv , sync clock ,hosting the sequincer and midi controller software to handle much else .... Etc .
Now you can certainly do this without a computer however , It would just require buying or building a suitable host . The iConnect midi 4+ , Kenton midi to usb host are it afaik in the buy it category . In the DIY part of world a rasberry pi or arduino ( though I'm assuming that these are not an option for you ) could do the job as well . Ironicly or in contradiction the latter are technically computers lol , but can function headless ,and for the midi 4+ you would require a computer or iPad for initial set up . Anyway that said there are options that don't require lugging around a laptop or the like , however even with that keep in mind you would limited to sync ( keep in mind the OG doesn't even have all the same quantizing options ) , and sending midi start / stop for simply one more 16 step part and the hardware connections that come with it .
