@eucador Crucial has confirmed that this laptop can support 20GB RAM. Crucial confirms this by performing real world tests.
As for the memory, it should still support dual channel mode.
Sources:
[link|https://www.crucial.com/compatible-upgrade-for/lenovo/ideapad-310-(15-inch)|https://www.crucial.com/compatible-upgrade-for/lenovo/ideapad-310-(15-inch)|new_window=true]
[link|https://www.crucial.com/compatible-upgrade-for/lenovo/ideapad-310-(15-inch-touch)|https://www.crucial.com/compatible-upgrade-for/lenovo/ideapad-310-(15-inch-touch)|new_window=true]