It is necessary to note, however, that the great filter does not necessarily occur when a civilization achieves some arbitrary technological level.

In fact, it could be at the point of single cell --> multi-cellular organisms or at the point of sexual dimorphism or developing general intelligence and ability to use tools, etc.

I guess it's also possible there are multiple Great Filters...

That's a good point, and you're right of course. In fact I take some hopeful comfort in the notion that while the leap from organic molecules to single-cells might not have been too big, there are some indication that going to multicellular life was a leap that took quite some time. We still have reasons to hope, but we're doing almost all that we can to extinguish that hope.