How to find out if I am using wayland or X11?

Find out the session ID

loginctl

SESSION  UID USER            SEAT  TTY
      4 1000 <YOURUSERNAME>  seat0 

1 sessions listed.

Session ID seems to be “4” in my case.

Display the the type of session

loginctl show-session <SESSION_ID> -p Type

Type=x11

Handy oneliner:

loginctl show-session $(loginctl | awk '/'"$USER"'/{print $1}') -p Type

~~DISCUSSION~~