Firstly, and most obviously, you have to HOLD "E" on intractable objects instead of the usual press from 2033 and Last Light. This now includes ladders and pathways that are too small to crouch into. You will also need to hold the necessary key while interacting with the objects we'll go over, excluding the "Throwables", which instead use mouse movement.

Also, you can now hold "R" to rip the attachment off a gun.

Secondly, if you would instead like to enable your hud without restarting, you can do so by going to user.cfg in your files and make the following change:

"g_ranger_hud_alpha 0." to "g_ranger_hud_alpha 1.".

I recommend using Ctrl + F and searching "hud" as it should be the only result.

I've been playing the Enhanced Edition, so results may vary, but here is the directory I had:

C:\Users\Username\Saved Games\Metro Exodus\(sequence of numbers)

If this directory doesn't work, you will have to search file explorer for "Metro Exodus", it should be the only result that doesn't include "Steam" or (for me) "Nvidia" in its directory path.

W = Drink whatever is on the desk, or simply pick up and then put down an empty cup.
A = Leave desk.
S = Check Artyom's Diary.
D = Access the radio.

Use the "A" and "D" keys to tune the radio.
Holding Right Click will turn off/on the radio.
Holding Left Click will return to the desk.

The most simple of the bunch.
Hold "D" to advance to the next location.
Hold "A" to leave the map.

Unlike 2033 and Last Light, you now need to hold "C" instead of holding "Tab" to select your throwables. While holding "C", you then need to move your mouse in the direction of up/down/left/right to select a specific weapon.

Up = Throwing Knives
Left = Grenades/bombs
Right = Molotovs/firebombs
Down = Decoys

W = Get up
A = Skip to night
S = Drink from your Trusty Vault 13 Canteen
D = Skip to day

Hold "D" to continuously shovel
Hold "A" to leave