All potentially for sale systems, including Y-20. There's a J-20 model though, so maybe only a portion is export approved.
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This is likely a diplomatic reception in Algeria where China's achievements are being shown off. It's highly unlikely that all or perhaps even the majority of the systems on display are being made available to Algeria. That said, the purpose of such exhibits is to increase a potential customer's confidence in China's technological and engineering capabilities, thereby making it easier to market various systems China does wish to export, such as UCAVs, radars, SAMs, etc.
By the way, I think that Twitter user Húrin is untrustworthy and should be avoided.