GIMP Version: 2.8.10
Operating System: Linux
OS Version: Fedora 34
GIMP Experience: Basic Level

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Having moved from GIMP 2.8 to GIMP 2.10 I found that the script directory/folder had changed.
To find out where it is - or to change it - use Menu action
Edit -> Preferences -> Folders -> Scripts
I found it was now ~/.config/GIMP/2.10/scripts
(My user script breaks large images up into A4 printable blocks.)

I have 2 directories as you can see on the screenshot
Maybe you just need to add your "older" path/directory beside the new existing one (as example, mine see below the directory "2.0" from GIMP 2.8 or may be even from 2.6)
To add a new path/directory click where the red arrow is pointing
Then things should work when you'll restart GIMP

Good point. In my case I had completely wiped by filestore and was rebuilding from documented codes but this will help others upgrade.