Seriously, just buy a good CRT. Stop fooling around with all this line doubler crap
Fancy upscalers and scaling filters can make retro games look (debatably) better on modern displays and maybe for some people that is good enough. But it's hard to beat a Craigslist CRT for an authentic classic gaming experience. Thankfully, there's still plenty of 'em that haven't been dropped off roofs, used for target practice or shipped to the third world for "recycling".
Eventually when the cheap used CRT supply dries up, with luck we'll all have cheap 4k OLED displays and CRT emulation won't look like such a steaming pile of dog shit.