"I don’t know if it can be processed locally but for such good results a cloud based system would be acceptable. I suspect it is using cloud based AI at present. I don’t think the shirt is problematic considering the starting point. "
Well I’m not ready to upload anything to cloud on another companies computers. For privacy reason and because that kind of business model puts the leverage way to much on the one side, leading to all kind of nasty behavior for the companies later down the line. It has happened in every situation.
As for the results. You say its acceptable, I find it not acceptable for anything other than casual non commercial social media experiment. The quality is no where near where it should be to have photograph quality, and if the goal is to make something look like it was processed by some filter, I would probably use different filters.
Output is relative to the input. And n this case it is a bit ambitious to try to take the image you started with and make it same or better at 6x enlargement. Even the original is pretty low quality , but 2x maybe you can get away with. But not 6x. That is way too much information to invent out of already not good starting point.
With high resolution, clean full of details file you might be able to enlarge it 6x in some cases, depending on what is in the image, but at the moment 2x is acceptable, everything above that tends to be either marketing or super low quality standards.
Just my 2 cents.