And I ran into the next thing I'm unclear about; I'd be glad about some guidance on how we're handling the dropping of old Qt5 packages.

I looked at quaternion-qt5, which fails to build: https://hydra.nixos.org/build/297643965
...because it uses libquotient, which has dropped Qt5 support: https://github.com/quotient-im/libQuotient/releases/tag/0.9.0
...which also seems reflected in the quaternion project's own CMakeLists.txt: https://github.com/quotient-im/Quaternion/blob/dev/CMakeLists.txt#L64
They seemingly just didn't update their readme and GitHub tags.

Should I just open an issue to drop the Qt5 version? Should I prepare a PR? Are there any policy-decisions to this (dropping an old package)?
Also: I guess with the Qt5 version gone, we could get rid of the -qt6 suffix, too. I'm not sure about how much potential there is for refactoring because of that.

I have an interesting problem when accessing https://hydra.nixos.org
With both Firefox and Chromium I get 403 responses and can't use the website. I've now debugged it with cURL and found the following.

Chromium: curl -I 'https://hydra.nixos.org/' -H 'user-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36'

Firefox: curl -I 'https://hydra.nixos.org/' -H 'User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:132.0) Gecko/20100101 Firefox/132.0'

Removing Firefox/132.0 from Firefox's headers fixes the problem. Removing Chrome/130.0.0.0 from the Chromium headers also fixes the problem.
To me this sounds like the firewall is too restrictive. I've now modified the headers with a browser extension to work around the problem.
Could someone fix this issue?