I want to create a custom Xmonad session that loads an .xsession script in my home folder.

This is the original file I copied. This one works:

[Desktop Entry]
Encoding=UTF-8
Name=XMonad
Comment=Lightweight tiling window manager
Exec=xmonad
Icon=xmonad.png
Type=XSession

This is my modified file, xmonad-custom.desktop. When I logout, then login choosing this "xmonad-custom", the screen just flashes and sends me back to the ubuntu login screen (as if it briefly logs in and out of the session):

[Desktop Entry]
Encoding=UTF-8
Name=XMonad Custom
Comment=Lightweight tiling window manager
Exec=/home/{username}/.xsession
Icon=xmonad.png
Type=XSession
X-Ubuntu-Gettext-Domain=gdm

I also tried without the last line.

This is my ~/.xsession file, in case there's an error with this script:

#!/bin/env bash

xrdb -merge .Xresources

trayer --edge top --align right --SetDockType true --SetPartialStrut \
true --expand true --width 15 --height 12 --transparent true --tint 0x000000 &

dropbox start &

exec xmonad