And it was based on Debian. Installing an "app" was quite literally installing a deb package. Back in the day, I was working at a mobile software company and they had to call the IT guy (i.e. me) to explain how packaging works in Debian, just for the new Nokia they sent us, about a month before official launch. I tought the gadget was adorable.
I still like to think of a parallel time line where Symbian actually had a good and usable app store, and developers had been supported.