Comment 5 for bug 1709881

If you're advanced user and don't mind to use the ppa-purge tool from pure console mode in case something goes wrong, there's (nowadays abandoned but Qt should be functional) PPA at https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/stable-phone-overlay/ that contains Qt 5.6.2 for Ubuntu 16.04, including qtbase compiled with -opengl es2 for arm64.

You should be safer if you try the PPA out from a desktop environment that doesn't strictly depend on Qt 5 - while the Qt itself in that PPA should be as functional as before, some Stable Release Upgrade that has happened after April 2017 may have made eg KDE Plasma or LxQt incompatible with the PPA.