We have released Qt 5.15.4 LTS for commercial license holders today. As a patch release, Qt 5.15.4 does not add any new functionality but provides bug fixes and other improvements.
Compared to Qt 5.15.3, Qt 5.15.4 contains about 100 bug fixes and security updates. The list of fixes and the overview of all important changes in Qt 5.15.4 can be found from the Qt 5.15.4 release note. It is available via Qt Account Downloads.
You can add Qt 5.15.4 in the existing online installation by using the maintenance tool or do a clean installation by using the Qt Online Installer.
If you have any problems with the commercial LTS releases, please contact Qt Support. You can also create bugs to https://bugreports.qt.io, but in addition it is recommended to notify the support team about it.
The next commercial-only LTS patch release, Qt 5.15.5 is planned to be released in June and Qt 5.15.6 will be released in August.