I'm gonna give this a try. I have a samsung and the camera app has glitchy slow motion for years. I would never buy another one again, but if i can get functioning slow motion then i can still use it at least for side projects

It depends on the phone camera API. Some allow up to some fps and the highest option is available through some vendor API that's not public. At least on mine.

The problem with the slow motion isn't the software, it's the phone.

Source: I have a Samsung phone. Any software trying to take slow-motion video glitches out. The camera also tends to make the phone overheat.