I have tried EVERYTHING I could to use the ST with my OSSC, absolutely nothing works. I've tried STf, STfm, STe models, PAL and NTSC ones. Nothing comes through. A friend of mine, electronician and well versed in retro consoles and computers, has modified my SCART cable twice for it to work, even adding a 75ohm / TTL switch. Nothing works. At least, thanks to the cable mods he did, it works now on my Sony PVM, I can use any ST model, which was not the case before.
I'm really disappointed since all my other retrocomputers and consoles work without any trouble on the OSSC . BTW I've also tried it on a Framemeister, same result !...