The easiest way to capture RGB scart is to get a scart to hdmi converter then use a decent capture device on the pc with hdmi input. Something like a Hauppauge PVR2 or similar. You can use these to capture composite and component out of the box but the picture quality on composite is not very good imo.
Another way is to use standalone HDD/DVD recorder, most of the european models come ready with scart inputs and can take in multiple types of signals ranging from composite to RGB. Only possible issues that comes to mind are that you can't probably achieve proper HD quality caps and might get bad results with non-standard refresh rates, but the outcome vary between different models and their specs being kind of hit and miss without opportunity to actually try them out. I have such a Panasonic unit (re-badged Pioneer, actually) from few years back, I haven't tried it with any old gaming/computer hardware but in general the most important negative point that stands out is that even when it can achieve very high bitrate with HQ record settings the resolution is always SD due to limitations of DVD format.