Just starting with Kdenlive. Installed v19.08.2 on a Windows 10 64 bit laptop, got the corrupted GUI issue. Then spotted the advice to downgrade to .6709 but on installing get the message

"Error
The driver being installed is not validated for this computer. Please obtain the appropriate driver from the computer manufacturer.
Setup will exit."

Any advice?

maybe you can't ... on past months we have seen another (NEW) laptop with only the latest intel driver on driver support page... (and old drivers are not working on the vga card)... the only thing i can say is to find the hardware ID of your VGA adapter .. and search a windows 10 (old) driver using this value... maybe from some other brand (dell,acer,lenovo,hp,asus) support page.

BTW what laptop is?

It's a Dell and probably less than 5-6 years old, but don't really know the details beyond that. But it was rebuilt earlier this year so think it's probably got quite new drivers.

How often do new versions of Kdenlive come out, and should I just wait to see if the GUI thing is resolved then?

what model of Dell?