I can't think of anything relevant changed in Qt itself since 5.5.1 landed in xenial in December, so it must have been some other package.
You may want to test Qt 5.6.0 to see if that gives any further improvement https://wiki.ubuntu.com/Touch/QtTesting
The current plan would be to have Qt 5.6(.1) in xenial-overlay eventually.
I can't think of anything relevant changed in Qt itself since 5.5.1 landed in xenial in December, so it must have been some other package.
You may want to test Qt 5.6.0 to see if that gives any further improvement https:/ /wiki.ubuntu. com/Touch/ QtTesting
The current plan would be to have Qt 5.6(.1) in xenial-overlay eventually.