I do not know if there is any reason in 2021 to consider legacy transcoders from yesteryear. We have great options now.
I also had a CSY clone and I was able to get it dialed in so that most things looked more or less okay, but it just was never very accurate as far as colors go. I worked hard trying to dial it in right. Just when you think things look good, you see a screen that you know should be pure white, but it's pink now. Damn.
Mike Chi makes a converter called 'RGB2COMP' for about $70.
https://www.retrotink.com/product-page/rgb2comp
I've had great success with my LinuxBot3000 transcoder, which I love and recommend above all other options. Everything that I have thrown at it looks perfect and the colors are always super-accurate. I have given it 15KHz RGB from eight different video game consoles and it handles everything perfectly. It even likes my Neo Geo CD, which the OSSC will not detect no matter what cable or input I use. The image is sharp. Mine uses USB-C for power, which I like a lot. He's got a few in stock as of the time of this post for $60.
https://www.ebay.com/itm/RGB-SCART-to-Y ... 4166352622
Another great option that I scanned the thread for and did not see mentioned is the GBS-Control project. You know that thread that is always towards the top of our board with 133 pages? If you are able to solder, you can put one together for about $40. It does a beautiful job and produces a crisp, color-accurate image with zero lag in transcoding-only mode. And, as a bonus, you get a more-than-decent video game scaler (there is about a half frame of lag when scaling). You do not need to do the clock-generator mod to use the transcoding feature. One thing to note however is that it hated my Dreamcast. It played nice with everything else, though, and I had fun sending a DVD to it over component to be downscaled to 240p for display on my tv. It has a few neat features that are nice to have access to.
Anyway, buy the LinuxBot3000 transcoder right now before he runs out and you have to wait a few months.