As you suspect, my laptop is dated. It's a Dell Latitude e6410, It's i5 intel (M520) processor and it's Windows 10. The GPU on the other is only stated Intel HD Graphics, which doesn't support OpenGL :(
I did some research and it's possible to force the engine to run using a slightly older version of opengl. Maybe you can give it a try.
You'll need to create a shortcut in the same folder as the game executable that runs this command:
CustomBallMerge_Windows_0.4.0.exe --rendering-driver opengl3
Please let me know if it worked for you!
Option 1: The quickest way is to open notepad, paste the command in the text file and save it as "CustomBallMerge.bat" in the same folder as the game.
Make sure it saves as a bat file (*.bat) and not as a text file (*.txt)
Then, just double-click the bat file to run the game instead of the exe file.
Option 2: Right-click on the game exe and select the "Create shortcut" option. Then right click the newly created shortcut and select "Properties" option so you can edit it. In the properties window, go to the "Target" field and add at the end --rendering-driver opengl3
Screenshot below for reference (my PC is in Spanish, but I hope it helps you to know where to look)
Then, just double-click the shortcut instead of the exe to launch the game.
OK. So after spending 9 hours recreating the whole game from scratch in Godot 3.5 (older engine version), I managed to get it running... but there are way too many bugs to fix for it to be in an acceptable condition.
Unfortunately I can't spend any more time on this "engine downgrade" experiment to get the game to work on older hardware. I really didn't expect there would be sooooo many changes between versions and that it would take so long to get to this half-done point.
If I manage to get some free time from my other projects, I'll try to get back to this and fix the bugs, but it's very low priority right now.