Broken out-of-the-box experience with the Qt installer for Qt 5.15.9 on supported platforms

Core issue

Trying to install Qt 5.15.9 on Ubuntu 18.04 (which is a supported combination) – either using the online installer or using qt-enterprise-linux-x64-5.15.9.run – will produce a cryptic error dialog:

Installer Error

Error during installation process (qt.qt5.5159.gcc_64):
Execution failed (Unexpected exit code: 1): "/home/USER/Qt5.15.9//Tools/QtCreator/libexec/qtcreator/sdktool addQt ...

There is no indication on why the error occurred, or what the customer needs to do to resolve it.

Furthermore, even if the user ignores this error, they're still forced to install a copy of Qt Creator that won't run.

Other notes

• This issue is not the same as QTIFW-2259 or QTBUG-88833 which were about installing Qt 6 on unsupported platforms.
• This issue is about installing Qt 5.15 on supported platforms.

The console does provide more details, but not everyone will see it (e.g. if they double-clicked the installer on the graphical shell):

Warning: /home/USER/Qt5.15.9//Tools/QtCreator/libexec/qtcreator/sdktool: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.28' not found (required by /home/USER/Qt5.15.9//Tools/QtCreator/libexec/qtcreator/sdktool)

Suggestions

Ideally, please let the installer provide a copy of Qt Creator and sdktool that does not require glibc 2.28 until Qt 5.15 reaches end-of-support.

If that is not feasible, then please do one of the following:

• Make the installer check the user's system and warn the customer if it is too old.
• Make the installer explain clearly what the customer should do instead, when faced with this error message.
• Document clearly that the installer no longer fully supports Qt 5.15 and its platforms.
• Remove Qt Creator as a mandatory component of the installer (QTBUG-28101, QTBUG-96148).

Workaround

1. Repeatedly click "Ignore" on the error dialog. This causes Qt 5.15.9 to be installed without being registered.
2. Download the standalone Qt Creator 5.0.3 installer, and install it to a separate directory.
3. Run Qt Creator 5.0.3 and go to "Tools" > "Options..." > "Kits".
4. Manually add your copy of Qt 5.15.9 as a Qt Version: https://doc.qt.io/qtcreator/creator-project-qmake.html
5. Manually add your copy of Qt 5.15.9 as a Kit: https://doc.qt.io/qtcreator/creator-targets.html