I'm on a Debian 12 system lacking a GPU (it relies on software rendering only) and trying to get running an email application (https://github.com/akissinger/dodo) which uses PyQt6 and QtWebEngine. The main window of the application and its basic functionality loads correctly, however when trying to perform a particular action (viewing the contents of an email inside a new panel/tab), the following error log is printed (after enabling QT_DEBUG_PLUGINS=1):
qt.core.library: "/home/user/dodo/.venv/lib/python3.11/site-packages/PyQt6/Qt6/plugins/xcbglintegrations/libqxcb-glx-integration.so" loaded library
qt.core.library: "vulkan" loaded library
Failed to create Vulkan instance: -9
Failed to create platform Vulkan instance
Unable to detect GPU vendor.
As a result, the respective functionality fails (the tab itself is created correctly, but the email contents aren't displayed). I've not been able to get rid of this error, although I've tried the following:
QT_QPA_PLATFORM=xcb
QT_VULKAN_DISABLE=1
QT_OPENGL=software
QTWEBENGINE_CHROMIUM_FLAGS=--disable-gpu
Any suggestions for how to force software rendering?
By the way, another application (https://github.com/qutebrowser/qutebrowser), which is similarly using PyQt6/QtWebEngine, is working fine on the same system (i.e same system-wide packages, otherwise the applications use separate Python virtual environments).