On further digging, I've found that this issue is due to an AppArmor rule, which for some reason was treating localhost differently (as IPv6) than a regular network address (IPv4). Closing.
** Changed in: xrdp (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to xrdp in Ubuntu. https://bugs.launchpad.net/bugs/1966048 Title: xrdp fails to bind to localhost To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xrdp/+bug/1966048/+subscriptions -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs