You mentioned your lack of interest in PhD program despite already 1.5 years into it. You might want to dig deeper into yourself to understand why that is the case. When you say meaningful, do you mean something that will change the world.
If you love doing something but you don't get recognised for it, would that bother you? If you did get recognised for a work which you were not passionate about. Would you still find meaning in it.
When you get more honest with yourself, the easier it will be to find the work that is meaningful. If you are not, then it might take years and you might only to bouncing from one work to another.
After I completed by engineering, I started a company with my friends - thinking this will be meaningful experience. And it was in many ways. It helped me understand myself and the world better. But, it took many years to figure out exactly what I wanted to do and where my heart lies. Most people don't take that journey.
So, if you want to find meaningful work, you need to start on the self exploration journey. Hope that was useful.