How EndeavourOS managed Gnome window decorations on QT apps?

When you run Gnome without qgnomeplatform or qadwaitadecoration window decorations of QT apps look like these (window on the right):

But on vanilla EndeavourOS, all QT and non-GTK apps have Gnome-like decorations.

Can someone please explain which settings EndeavourOS use for this?

My system haven’t any additional installed libs, also I’m checked installed packages and environment vars, none of these packages mentioned above never installed.

Is EOS used some patched libs?

Welcome to the forum @linux_user ,
I cannot confirm this vanilla state.
(I had problems with íMercury iso Gnome install so I used neo and updated).
With the help of
yay -S gnome-tweaks
you can move on, perhaps.

Thank you for the help. I’m only switched buttons placement through gnome-tweaks settings and apply theme for QT apps. But when you installed pure Arch Linux, QT apps (like Qbittorrent for example) wouldn’t have top bar in Gnome Adwaita style.
Thank you for advice about Neo iso, on previous release I’m not faced these changes. But I’m wanted to be figured out how this can be implemented on current release without additional libs or where these setting are stored, because I didn’t find any configs files or environment vars.

AFAIK these settings are stored in
~/.config/dconf
It’s a binary file.
yay -S dconf-editor
helps you to see and modify (with care).
/ org / gnome / desktop / wm / preferences / button-layout
colon separates left and right as it is described.

Thank you for the help! I’m really appreciate it. But maybe I’m bringing some misunderstanding here. Sorry for this, English is not my native language. I’m talking about this thing in Gnome: https://jgrulich.cz/tag/adwaita-qt/
Since one of previous Gnome release, server side decorations were dropped, and not supported anymore.
For replace this was developed special library - qadwaitadecorations https://github.com/FedoraQt/QAdwaitaDecorations
But EndeavourOS don’t provide this library by default, though functionality of this library somehow implemented in system. And I really want figured out how this implemented in EOS.