Startup/boot script with systemd issues

I found a solution. Thanks for your help @AastaLLL.

It looks like it was my service script that was the issue. I added XAUTHORITY and DISPLAY and it works great now. ExecStartPre was also added just to delay the start of the script but wasn’t the reason for it working.

Working code looks like this:

Description=Execute this on boot

ExecStartPre=/bin/sleep 10
ExecStart=/usr/bin/python3 /home/ag72/Startup/