You can get GPUs as new as Nvidia’s GTX 900s and AMD’s R9 300s which will be DVI-I capable (DVI-I or DVI-A are what you’re looking for, not DVI-D). You can then use a DVI to VGA to composite adapter chain for perfect, lagless CRT video output.

It is not compatible with Linux and IIRC the dev does not know how to port it.

I’ve seen a bunch of people recommend this and I’ve played around with it a bit since they initially added frame gen to Lossless Scaling. It never feels smooth. There’s always some stutter/jitter in the frames that makes it feel terrible, even when it’s “100+ fps”. Definitely feels worse than a native 60. Also worse than AMDs fluid motion frames option which does feel and look smoother. I leave it installed and come back from time to time to see if it’s improved but it’s just not something I’ve found to be enjoyable or an improvement to my gaming experience.