.well-known won’t exist in the deploy as dot files are ignored. As explained in this post the workaround (as you have tried) is to create a rewrite. However this rewrite
[[redirects]]
from = "/.well-known/apple-app-site-association"
to = "/.well-known/apple-app-site-association"
status = 200
force = true
as from the blog you linked won’t work because it is writing to a non-existent dot file (directory).
The rewrite Hrishikesh has demonstrated will work if the file exists at the site root. If the apple-app-site-association/apple-app-site-association.json file exists in another location, change the path accordingly. If it is inside a .well-known directory, rename the directory (to anything you desire, but ensure it doesn’t start with a .) to ensure it is published.