secrec System Settings --> Display --> Night Light
Meh - To some Greyscale is way better (or can even do both) - but Night Light at least has short cut.
taivlam , this is only available through Digital Wellbeing, which is provided through stock Android with system-level Google Play Services.
yes - it's one of those things I miss from my former phone but you can make yourself an own "bedtime mode"
-set "Do not Disturb"
-get easy access to Night Light and/or Grayscale*
You basically have Bedtime Mode :)
(*I wish you could set a quick access button without involving the rest of Accessibility)