I'm very new to Orion and not a technical person but I was able to get StopTheMadness installed and confirmed it works. I have a paid pro version, so assuming you have that...
Open the StopTheMadness Pro application on your Mac.
Click on the Chrome install (in the StopTheMadness app, not Orion)
It says to open Developer Tools, but your only option is to "Install from Disk" in Orion's Extensions Manager.
Select Save here.
At this point the install process can get a little difficult.
You need to click and drag over the icon from the StopTheMadness install box into the open dialog box in Orion.
That transfers the files (as best as I can recall) and that seems to install it, but...
I just tried this on a fresh install in another user account I have on my Mac, and kept getting an error message until I clicked on the StopTheMadness icon in the toolbar, which seemed to make it work.
Without a Developer Mode to install extensions from disk, it's a bit hit and miss, but StopTheMadness can be installed if you're willing to deal with some frustration.
I tested it to disable displaying of Youtube shorts, to turn on/off native video & audio controls, and stop autoplay, all of which work within Orion, so I know it works once you get past the difficult installation.