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Is it normal for qt5 to take hours to upgrade?
Yesterday I gave up on an upgrade from qt5-5.7.1 to version 5.12.8 because it was already taking 14 hours to install. The OS is Slackware 14.2, the notebook has 4G RAM, and only this installation was being performed at the moment.
Where you using the Maintenance Tool for that ? If so, you might have been hitting a faulty mirror.
I am using the following command, where I mean it is from the slackbuilds repository:
slpkg -s sbo qt5
So it's a problem of your distribution.
I removed the old version and installed the new version without WEBENGINE, and it worked.