To do this, go in Settings, then `Accessibility > Color and motion > Color correction`, and set it to grayscale.

While still in the `Color correction` submenu, click `Color correction shortcut`, set it to `Hold both volume keys`, and toggle it on.

I just discovered this myself, but with the ability to quickly flip it off when needed (taking pictures/watching videos/etc) I may actually end up keeping it enabled this time around.

If you want to play around with the other options (or permanently set greyscale), it’s under Settings —> Accessibility —> Display and Text Size —> Color Filters. Or just search Color Filters from the main Settings search bar.

Color Filters also has a true no blue mode for night.

Turn that on and then you can select "Greyscale" as an option. I have this mapped to the double tap the back of the phone with an accessibility shortcut.

Basically I can double tap the back to toggle greyscale mode.

Setting -> Accessibility Display & Text Size Colour Filters

edit: Shoulda refreshed before I commented...

I deleted all social media apps years ago.

I’m doing fine most days.

I never liked any apps on the screen when I had Android, and liked (and still like) its swipe-for-app-drawer mechanism. It’s unfortunate that on iOS it’s more difficult to have a clean Home Screen, and no options that I’m aware of to get the Android launcher actions.