For an avid photographer, which cellphone is better between Google Pixel 3A, OnePlus 7T and Samsung S10?

I suggest a good rangefinder. They are small and the image quality will be much higher than using a phone. I know that isn't what you were asking for but I am not a fan of phone cameras.

I agree with this answer. If photos or photography is important to you I would highly recommend almost every small camera over a phone. Pretty much every small camera lets you change settings like aperture and shutter speed. I also find a camera much more enjoyable to use than a smartphone. Smartphones also tend to brake faster since they dont offer any kind of real grip and are picken up much more often. How long do we stick to one phone? I cant remember that I sticked to a phone longer than four years but I still love my old Nikon which I got in 2007.

In my expectation phones also alter your image based on optimization algorithms which you might not like. A real camera might give you more control over your image. (I dont have any particular models in my mind - I just compare my phone versus my cameras for photography for myself to answer this).