GNOME Wayland session?

I’m running into a weird thing where GNOME is using X, rather than Wayland, under 19.09 (clean install). I remember under 19.03 that there were two sessions, one for X and one for Wayland. But now I just see one session, and it loads me up in X.

Pocking around a bit, it looks like gnome-session is dropping a gnome.desktop file in both wayland-sessions and xsessions, so I wonder if I’m running into some variant of Ticket #56342 (lePerdu describes something there that sounds like what I’m experiencing). I only see a single session available for GNOME in GDM, and it corresponds to gnome.desktop (the files in wayland-sessions and xsessions are identical).

Anyone else experiencing this? Does anyone know if other distros have duplicate gnome.desktop files in the two session locations?

In case anyone else runs into this, here’s what my problem was:

I’m importing <nixpkgs/nixos/modules/profiles/hardened.nix>, and then tweaking a few settings that don’t make sense in a desktop context. It used to be that one of these tweaks was to set security.hideProcessInformation = false, as otherwise this would break GDM. However, in 19.09 hideProcessInformation includes a few tweaks that let GDM work.

But! Having hideProcessInformation set to true still turns out to break a set of other things in subtle ways, including the ability of non-root users to spawn Wayland sessions.

TL;DR Make sure that security.hideProcessInformation = false; if you want GNOME to be able to run a Wayland session.