I use it almost exclusively/when it makes sense to. But so many people are surprised that I use it.
Part of it is because I was an android user until about 2015 and that was always a feature on the phones I had. I also use it because I have small hands and the biggest iPhone so I find it easier to type one-handed sometimes.
Since swiftkey first appeared on android - so probably at least ten years. It makes a lot of mistakes though. The most frustrating one is that it seems to struggle with the word “and”. Apparently it believes I must mean “ABS”. I guess ABS is far more likely than “and”. /s