Switched from Xperia X to Xperia 10 III - and figured out neither the “Night Silence” app nor “Situations” are available, probably because the Xperia 10 III is aarch64.
Is there any way to automatically stop the phone making any noise at night (and automatically set it to “loud” in the morning again)?
Is the source code of “Night Silence” somewhere available?
Situations runs just fine on aarch64. Not sure what the problem here would be.
You may also try Ringing Restorer (but I have never used it).
Alternatively, one might simply use a pair of systemd services/timers:
~/.config/systemd/user/dnd-activate.service
[Unit]
Description=Do-not-Disturb mode toggle
[Service]
Type=oneshot
ExecStart=/usr/bin/dconf write '/lipstick/do_not_disturb' 'true'
~/.config/systemd/user/dnd-deactivate.service
[Unit]
Description=Do-not-Disturb mode toggle
[Service]
Type=oneshot
RemainAfterExit=no
ExecStart=/usr/bin/dconf write '/lipstick/do_not_disturb' 'false'
~/.config/systemd/user/dnd-activate.timer
[Unit]
Description=Do-not-Disturb mode Activation
[Timer]
OnCalendar=Mon..Fri 23:59
OnCalendar=Sat,Sun 01:15
Persistent=true
[Install]
WantedBy=timers.target
~/.config/systemd/user/dnd-deactivate.timer
[Unit]
Description=Do-not-Disturb mode Deactivation
[Timer]
OnCalendar=Mon..Fri 06:30
OnCalendar=Sat,Sun 08:30
Persistent=true
[Install]
WantedBy=timers.target
After creating these:
systemctl --user daemon_reload
systemctl --user enable dnd-deactivate.timer
systemctl --user enable dnd-activate.timer
systemctl --user start dnd-deactivate.timer
systemctl --user start dnd-activate.timer
That is true, fixed now! 
You’re right: Situations is available in Jolla Store. My bad. Thanks!
Then you can simply use ambiences to automatically stop the phone making any noise at night. 
That way the silence mood also gets very visible.