I’ve had some success on Match, though I canceled my subscription and hid my profile last May when I was starting to become more sick and didn’t think I was in a good place to be dating anyone. You pretty much have to pay for a subscription if you have any hopes of making contact with another member. I’ve seen women on there use clever ways of including contact info undetected in their profile so they didn’t have to pay, including my ex-gf, but I usually avoid those since I figure most are scammers.
I would never put anything about my illness in my profile, though. I save that info for just a little while into dating, after she’s had a chance to see that I’m a good guy, hopefully realizing that I’m not dangerous. Most people have major misconceptions about people with MI.