Digitizing Super 8 movies

Hello,
sorry, what you’re asking is almost impossible to achieve.
To eliminate the flickering, you would need to project image by image and film image by image. Personally, most of my Super 8 films were shot at 24 fps. Since I found a transfer box for a ridiculously low price, I went ahead and tried filming with a camera at 24 or 25 fps, but it still flickers.

The flickering issue comes not only from the lack of synchronization but also from the small shutter that rotates during projection 2, 3, or 4 times faster than the images to exceed the persistence of vision. Of course, this is totally unnecessary and even detrimental for a recording device (DSLR or camcorder), but it's difficult to eliminate because the film is likely to be damaged by the heat of the bulb. A very good handyman can solve all the problems, but it's really not simple.

The solution involves an intervalometer that simultaneously triggers a projector and a DSLR (or camcorder) in frame-by-frame mode. Assuming it triggers at about 4 or 5 frames per second, the transfer duration would be multiplied by 4 or 5 depending on whether the shooting was done at 18 or 25 fps. So it's doable, especially since there is software capable of converting a series of images into a video. The challenge is to find a projector that can be triggered electrically frame by frame. This option was quite rare, but it did exist. Unfortunately, not with my projector.

Personally, I'm considering getting an editing viewer to select the best shots and assemble them together. Then have the film digitized by a specialized company, which could ultimately be less "costly".

The shimmer is not visible in the final result, I guarantee it.

why bother when you're not a specialist, photography stores do it.