So this was a problem caused by third-party PPA. If you want newer Qt, it is better to upgrade to a newer Ubuntu version (18.04 LTS has Qt 5.9, 19.04 has Qt 5.12), rather than use PPAs.
** Changed in: qtmultimedia-opensource-src (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1825485 Title: It requires two dependencies that are in conflict (libqt5core5a and qtbase-abi) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/qtmultimedia-opensource-src/+bug/1825485/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs