This version makes the new faster version of QAM for gamescope opt in, since valve broke it with gamescope 3.4.11, even on their own code. It also adds support for a bunch of Ayaneo 2021 models.
You can enable the fast QAM version with the following environment variable:
HHD_QAM_GAMESCOPE=1
Enter this into your /etc/profile, /etc/environment or a file in /etc/environment.d/qam.conf
If you disabled it previously with:
HHD_QAM_LEGACY=1
You do not need to do anything, if there is ever a change where it becomes opt out again, this variable name will be used again.
Full Changelog: v2.6.4...v2.6.5