It would be nice if Building Qt from source documentation for Qt6 can be more descriptive sighting common errors and solution:

For example.

1:

ERROR: Feature "openssl": Forcing to "ON" breaks its condition:
    QT_FEATURE_openssl_runtime OR QT_FEATURE_openssl_linked
Condition values dump:
    QT_FEATURE_openssl_runtime = "OFF 

in above case it should be mentioned that this error means Or Error it should say following:

"openssl at <default search location> not found, OPENSSL_ROOT_DIR not set"

2:

For Webengine https://doc.qt.io/qt-6/qtwebengine-platform-notes.html

It would be nice if the document says that CMake, Python, Bison, Flex, GPerf, Node.js etc should be added to PATH.

3:

And when adding this instruction to PATH it is important that to mention to not use quotes because it seems that Cmake has bug which considers

SET PATH=%_ROOT%;"C:\Program Files\Python311"; as

paths like C:\currentworkingdirectory\"C:\Program Files\Python311", which is invalid.

4:

several time during parallel build, where the build process aborted with a file access denied error. It seemed as if one job was still creating a dll/exe and had exclusive access to this file while another job was trying to embed a manifest in the binary.
Restarting with
cmake --build . helps.

5:

It is stated that html5lib is needed. Please add 2 more hints:

• How html5 lib is installed (using pip3)
• As it seems, it must be installed with admin rights, otherwise it ends up in a per-user directory, where it is not found by cmake

6:

It is already stated that "The path should also be kept short.". However, how short is "short"? Also, couldn't a cmake script check this beforehand and inform the user with a good message? The resulting error messages, if path length of 260 chars is exceeded, are not very helpful.

7:

Please add a hint, how much RAM is needed to build Qt6 (with and without WebEngine).
With WebEngine, 8GB are not enough. Had to install and prepare everything on another PC with more RAM.