Can be marked deprecated once we don't support Qt 5.12
According to https://community.kde.org/Frameworks/Policies
In addition, a Qt LTS release remains supported until the next Qt release after the next Qt LTS release. For instance, when Qt 5.15 is released, Qt 5.12 remains supported until Qt 5.16, to give time for people to migrate from Qt 5.12 LTS to Qt 5.15 LTS. When Qt 5.16 is released, both Qt 5.12 LTS and Qt 5.13 are dropped, to go back to "last 3 minor Qt releases".
That means we would support 5.12 until the end? Can we still mark it as deprecated sometime?