To train an AI to recognize handwriting you need a huge dataset of handwriting examples. That is millions of samples of handwritten text + information about what the written text says in every example).

then how can this model be so good? the dadaset is only 350 MB and the results seem insane … sadly i have no idea how to use it.

Premium domain is only available when you have premium, because fewer people pay and fewer people use it, so there is less abuse and the domain name has better reputation, so when you public domain is not working, using the premium domain may be able to register.-

And not that everything is a competition, but in my testing the results of upscayl always look a bit better than the ones from this web based non foss upscaler.