Setting up Retroarch for N64

Retroarch N64 core and configs

main menu > manage cores > Mupen64Plus Next
settings > drivers > video > vulkan

Get and save your roms

Create a directory on your system to save the .Z64 files
For this example we will use "/home/roms/n64"
Get N64 roms (i.e from r/roms megathread)

Import the rom(s)

Import Content > Scan Directory > /home/roms/n64 > (Scan this directory)
On the left sidebar menu will appear a N64 controller icon at the bottom.
Boot a game, press F1 to access the Retroarch menu.

Steam version controller setup

Steam library > RMB on retroarch > properties > Controller > Disable Steam input
Bind controller inputs:
Settings > Input > Retropad Binds > Port 1 Controls

Useful in-game controls

Press F1 > Save States > State Slot
Press Spacebar to enable fastspeed
Press F2 to save the current state
Press F4 to load the last state

Linux

You can find the retroarch config file file using
find ~ -name "retroarch.cfg"