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best
What do you mean by best? Coverage, evergreen, flowers?
I think a nice rambling rose is a good shout. Jasmine would have been my suggestion, but as you don't get sun then you probably want to try collins suggestions to me the other week:
https://www.lfgss.com/comments/15832807/
Star jasmine is also an option, although mine basically just survived when they were on the north side and took a million years to start to get going on the west side (heavy sun) and east side of the house. But they may have been a bad batch. Also I think I've had maybe 2 flowers. Although it does look nice now it's established on the front.
What are the best climbers for a south facing fence which never seems to get much light?