I honestly couldn’t care less about how the calculator app looks, and I’m sure you could find a more “modern” one on fdroid. The real problems are things like google pay not working (not a deal breaker imo, but would be nice to have)

I don’t think the radiation should be too big of a problem, they are in a very low earth orbit, well inside of the Earth’s magnetosphere. Not to say there are no health risks, they lose a lot of bone and muscle mass, but radiation shouldn’t be a big concern