Qt apps' title bar as generated by gnome (mutter?) do not match title bars of gimp, gedit. where do I report this bug?

[CapSel]

• Materia version: 20210322
• GTK3 version: 3.24.30
• Distribution (and version): archlinux "fresh"
• Desktop environment (and version): gnome 40.4.0
• Related application (and version): Audacious 4.1

In gnome tweaks I selected "Materia" variant - black title bar with rest white (or light grey). I also set up kvanum and qt5ct to use materia theme (I know - kde/qt not in this repo).
After freshly logging in (after power off or reboot) Audacious (and rest of Qt apps) starts with white title bar. All GTK+ apps, including gedit, gimp, inkscape, have black title bar.
White title bar on Audacious can be fixed by restarting shell (alt+f2, r, enter, using Xorg) or sometimes by selecting "Arc Darker" in gnome-tweaks and then returning to "Materia".

Is this the right place to report this problem?