Neon is still shipping SDDM 0.18.1. Even though SDDM isn't a KDE project, it's somewhat closely coupled to Plasma, and Plasma benefits from always having the latest SDDM version as if it was a KDE project. For example, BUG 432930 is only actually fixed when the SDDM version is 0.19. It would be nice if we could consider upgrading the SDDM version shipped in Neon to 0.19, and thereafter always ship the latest version as if it was a KDE project.
Blocked by https://github.com/sddm/sddm/issues/1358
Is it really blocked? Based on discussion in the bug report, it looks like you could work around that issue by shipping a /var/lib/sddm/state.conf file that specifies the X11 session as the default one.
*** Bug 433384 has been marked as a duplicate of this bug. ***
That is also tricky woo since that needs coding and testing by someone. Files don't just appear. Plus there's the fact that this is kinda a crutch and we really don't like crutches as they tend to break at some point.