Greg Egan's short story collection Axiomatic has some stories dealing with the issue of identity after upload. It probably comes up in some of his other stories as well, but that's all I've read so far of his works.
I like permutation city from Egan, for some more nice thoughts on the matter.
"Permutation city" is like the sacred book of uploading, in my opinion.
Absolutely, one of my favorite novels of all time.
Chiming in to join the chorus of praise for Permutation City and also call attention to Egan’s technical notes / FAQ for the same. Really mind-bending reading https://www.gregegan.net/PERMUTATION/FAQ/FAQ.html