Filippo Valsorda, the author of Age, is a qualified cryptographer and I can vouch for them, being myself an applied cryptographer. And many of my cryptographer friends do as well.
Age seems good to me BUT. I don't like streaming, and the article that you cite is on point. To me, streaming is unwise precisely because you can have truncation attacks. Or even length extension attacks. One may counter them using counters, but you will need a temporary storage until you know if the input is complete or not. And this defeats streaming.
Your application might be OK with truncation. That's for you to determine. Which is hard. If you can't decide, then you shoud stay away from streaming.
I wrote an article on this myself, a few weeks ago. I use that approach in production to secure some data that may be sent to me anonymously. It was reviewed by some cryptographers in my circles but I do not claim that it is a trusted library.