I use taskarou , an app in the play store, to give myself soft buttons on both the bottom and right sides. You swipe from the edge and they appear, then disappear upon release. The way the app is set up initially is way too confusing for me, with multiple sub menus, but now that I have just back, recents and home it is much better. There is no way to get the menu bytton without root on any app like this, but overall I haven't missed it to much.
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