Ok, Qt6 actually has Win10 as an official minimum requirement - earlier versions just didn't force it at compile time.
1) we need to make win10 the minimum requirement for Qt6-client, Qt6 modpack installer, and Qt6 ruledit (I think that will be what resolves this ticket; the build issue)
2) We can't drop Qt5 support from Windows environments etc, but instead implement that even to meson based builds. Relevant tickets to be created.
Reply To cazfi
1) we need to make win10 the minimum requirement for Qt6-client, Qt6 modpack installer, and Qt6 ruledit (I think that will be what resolves this ticket; the build issue)
Attached patch handles that for Meson. We still need a new ticket for autotools.
Building installer_cross / Meson Qt6-client with crosser from 2.5 branch (the branch is different from main, and current HEAD is already considered a crosser-2.5 candidate) gives
<command-line>: error: "_WIN32_WINNT" redefined [-Werror]
<command-line>: note: this is the location of the previous definition
Se it looks like in addition to our own _WIN32_WINNT definition we're inheriting one from somewhere else (presumably with pkg-config)
And that part of the command line is: "-D_WIN32_WINNT=0x0A00 -DWINVER=0x0A00"