@blipson FWIW, I have a Kenton MIDI USB Host Mk II, which lets me control the Aerophone AE-10 from a MIDI keyboard - not something I've wanted to do, but I tried it a while ago and that worked. I used a Yamaha CBX-K1, which has DIN MIDI Out and no USB.
@bibenu Yes, I was thinking people would be put off by reading this thread too.
AFAIK, the solution was the one posted by @hansgdaun, above, who deserves more credit for it than I do - I found the page that led to that answer, but he was the one that tested it and wrote it down in a clear way. Basically, it relies on using rsync, in a terminal window.
FWIW, I've put it off too, but mostly because I thought there might be minor updates afterwards, and I wasn't in a rush.
@Laurent_AODYO I'm glad @Lyricon was able to recover using that method, if so. Since these forum threads can be read by anyone, AFAIK, I think it's worth updating with the outcome, when someone reports a serious problem - for example if it's then resolved in a private conversation or by email.
@Laurent_AODYO Have you been able to solve the problems people have had in trying to install the update, such as Frank (@Lyricon ) had? Failing to update is one thing, but being left with a non-working synth unless it succeeds, is a much bigger problem.
@Clint Some electronic parts suppliers sell self adhesive copper tape, in a few different widths. It's also sold for shielding electric guitars, but more often in sheet form. A while ago, I saw it in pound shops (discount / clearance shops) being sold as slug tape / slug repellent tape, so garden centres might have some. You can find it sold on eBay too, of course, as some variation on "adhesive copper tape" or just "copper tape".
@wwoodard8 Nice. Yes, that looks like it's much better for ergonomics.
@hansgdaun You're welcome :) I'm glad you've got it working.
@wwoodard8 I don't own a sylphyo but octave buttons are always a problem. Having to move your left thumb around isn't really natural and means that fingerings in one octave are more comfortable than the same one in another. The EWI4000s, with its octave rollers, is the worst I've encountered, so far.
On my Yamaha WX5, I've stuck a small self adhesive felt disk on the larger central left thumb position, which helps a little. Raising it above the buttons seems to help, but also the roughness of the felt means I can get a better idea of where my thumb is. On my Roland Aerophone AE-10, I've cut a thin crescent shaped piece of self adhesive cork, to cover the first octave up button.
I don't know if that's practical on the syphyo, but maybe you could stick something to the left of one of the indentations, that you can feel as a reference.
@hansgdaun This doesn't appear to offer a solution, but it's a related problem, illustrating the fact that it's not limited to updating this particular device:
https://github.com/ARMmbed/DAPLink/issues/982
Possibly the simplest solution would be to find someone with a Windows PC that you can use to do the update.