Modern Retro A/V

I know this topic has been covered, but I can only find posts from 5-7 years ago, so I'm looking for some more recent information.

What is the best way to hook a retro system up to a modern TV? I have seen mentions of RAD2X, but I'm not paying double the price international shipping, I'd rather source an old CRT.

I also saw something about "RetroLink", but they lacked the information that the RAD2X has about how to hook up the unit and I'd really rather not be guessing and have to RMA things. The unit that was recommended for my model 2 Genesis doesn't even have a plug that matches the Genesis cables.

What are people using currently that is available in the US?