A better bet is probably a standalone composite to RGB converter. I’m not sure what’s available, but I imagine there must be some, somewhere.
(But if you (or anyone) does come up with a nice DIY converter, I’d be super interested! Here’s hoping!)
Oh and here’s an application note that I think it for a digital decoder, but has a decent explanation of how decoding has been done analogly: https://www.renesas.com/us/en/www/doc/application-note/an9644.pdf