When viewing lists of issues there are options to view the list as "Atom, CSV & PDF" output. The sorted content in the CSV & PDF output reflects the selected list settings in the current view, but that's not the case for the Atom feed. For my test instance with just a few Issues, the Atom list is always in descending order. Note that the same problem exists on this redmine.org site, but I can't work out what the sort order is here in the Atom feed - but it's not Ascending order, like I asked for.

My Environment:
Redmine version 4.1.1.stable
Ruby version 2.5.1-p57 (2018-03-29) [x86_64-linux-gnu]
Rails version 5.2.4.2
Environment production
Database adapter PostgreSQL
Mailer queue ActiveJob::QueueAdapters::AsyncAdapter
Mailer delivery smtp
SCM:
Mercurial 4.5.3
Git 2.17.1
Filesystem
Redmine plugins:
redmine_env_auth 1.1
redmine_language_change 0.1.0
redmine_wiki_lists 0.0.9