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My too, error compile QT5 via download gitlab fixes_3.0.zip, OS Kubuntu,
but, via download gitlab fixes_2,.2.7.zip success install with QT5
Thats because fixes_2_2_7 does not include some quite significant improvements that zeljko has made. I believe you most certainly want the better code in fixes_3_0. And that requires you to either use the newly compiled libqt5pas from
https://github.com/davidbannon/libqt5pas or to build and install them yourself, source and instructions are in the fixes_3_0 source code.
If you are building lazarus QT apps, you need both the library and the dev library, your end users will need only the Library. Right now, very few if any distros will have the up to date library in its repo. Debian, for example, will not have the new libraries anywhere in its repos until the version 3.0 of Lazarus is released.
David