As reported upstream:
https://gitlab.freedesktop.org/xorg/driver/xf86-video-qxl/-/work_items?show=eyJpaWQiOiIxNiIsImZ1bGxfcGF0aCI6InhvcmcvZHJpdmVyL3hmODYtdmlkZW8tcXhsIiwiaWQiOjU2NTg2fQ%3D%3D
Since the original report is 4 years old, it may not get fixed
upstream anytime soon, so at least in the meantime you may want to
fix it in Debian:
--- a/src/qxl_driver.c
+++ b/src/qxl_driver.c
@@ -995,6 +995,10 @@
memcpy (qxl->options, DefaultOptions, sizeof (DefaultOptions));
xf86ProcessOptions (scrnIndex, pScrn->options, qxl->options);
+ /* found is wrongly initialized with FALSE, also xf86ProcessOptions resets it to FALSE */
+ for (OptionInfoRec *p = qxl->options; p->name; p++)
+ p->found = TRUE;
+
qxl->enable_image_cache =
get_bool_option (qxl->options, OPTION_ENABLE_IMAGE_CACHE, "QXL_ENABLE_IMAGE_CACHE");
qxl->enable_fallback_cache =