So I have been using PopOS a ton lately due to my workstation doubling as a gaming setup, but XRDP just breaks after a while.
After doing some digging, and finding other people who had this issue but no solution, I decided to post what I found to fix the issue in case others like me come across this as well.
The issue stems from GNOME_SHELL_SESSION_MODE, GDMSESSION, and XDG_CURRENT_DESKTOP not being populated. We will need to fix that.
Edit file /etc/xrdp/startwm.sh:
sudo nano /etc/xrdp/startwm.sh
And add these lines to the very top (below the comments):
export GNOME_SHELL_SESSION_MODE=pop
export GDMSESSION=pop
export XDG_CURRENT_DESKTOP=pop:GNOME
After you add those lines, restart xrdp:
sudo systemctl restart xrdp
This fixes every box I have Pop installed on with xrdp installed.