Qt LTS commercial changes impact

I was catching on some news recently, when I stumbled across the following article on Phoronix. It seems that Qt is now making LTS versions only accessible when being a commercial customer.

I see that we follow current LTS version on NixOS, and that on 20.03 we’re currently merging with QT in version 5.12.

My question is : is there any guidelines on which version should be tracked upstream ?
I agree that we should follow LTS version as most as possible to limit the maintenance burden on all packages, but on QT case : could it mean that we could miss a security fix for instance ?

Qt offering changes 2020 has more details, in particular “LTS and offline installer to become commercial-only”. I’m not sure NixOS uses the LTS version on purpose.

@ttuegel Do you think you could commentate on this?

The policy for Qt support has been to carry versions until they are unsupported upstream. We do not drop versions sooner because other software (particularly proprietary software) that depends on Qt may depend on a specific version. We don’t intentionally carry versions longer than the upstream support window because, in general, Nixpkgs isn’t concerned with software that is unmaintained upstream. The changes to Qt offerings doesn’t really impact our policy, but we will probably stop simultaneously carrying multiple versions of Qt 5.

At present, we only support Qt < 5.13, not due to policy, but due to a lack of maintainer time. Qt 5.13 and later have significant changes to the build system compared to Qt 5.12, and our packages need to be significantly overhauled.


Thank you for your answer @ttuegel (and for the plasma maintenance ! :smiley:).

It means that the maintenance will now be more time-consuming since we cannot rely on the LTS channel ? On the blog post linked by @worldofpeace, they state that the new LTS policy will start with Qt 5.15, with 5.12 ending in december 2021, we’re safe for the 20.03.

On the maintenance side, what could somebody do to help you manage and update Qt ? Is there anything you would need help for ? I can dedicated some time if needed, I have some spare time I can take that I would be glad to dedicate to the NixOS community to help on this matter.

In general, I expect maintenance will be less time-consuming because we will not need to maintain multiple versions of Qt simultaneously.

We need someone to update the packages for Qt 5.14. This consists of basically two parts: updating the sources and fixing build failures. There are instructions to update the sources. Fixing the build failures will be more complicated. The patches will need to be updated, and that requires some knowledge of C++, qmake, and CMake. If the changes to the build system are as substantial as I believe, we will need to write new patches. There was an open pull request for this from a regular contributor, but I don’t think all the problems were ever fixed.

1 Like