Can you replace your gnome-settings-daemon executable with a script that calls the real (renamed) executable with the --debug argument so that we can see what's going on in the log output ?

Created attachment 337573 [details]
gnome-settings-daemon log with debug enabled

I noticed that this doesn't not occur right after boot. Presumably it's the gnome-settings-daemon attached to gdm that times-out and triggers the screensaver when a new session is opened because AFAIK it's sharing the same wayland display. Could it be something like that?

I was able to reproduce now after enabling session idle (which I usually keep disabled).

Created attachment 337662 [details] [review]
MetaIdleMonitorNative: initialize last event timestamp

If this isn't initialized and an idle watch gets instanced before
meta_idle_monitor_native_reset_idletime() gets called, that idle watch
would get triggered as soon as we hit the main loop.

This was causing gnome-session to go into idle mode at session start
thus making gnome-shell lock the screen.

In the past this bug was being masked by either logind emiting
session active signals or a stray input event making it through at
startup.

--

I suppose this was uncovered by a logind behavior change but I'm not
sure.

Review of attachment 337662 [details] [review]:

LGTM

Review of attachment 337662 [details] [review]:

Works for me too.

Attachment 337662 [details] pushed as 280e297 - MetaIdleMonitorNative: initialize last event timestamp