The following error appears:
CMake Error at CMakeLists.txt:13 (find_package):
Could not find a package configuration file provided by "ECM" (requested
version 5.246.0) with any of the following names:

ECMConfig.cmake
ecm-config.cmake

Add the installation prefix of "ECM" to CMAKE_PREFIX_PATH or set "ECM_DIR"
to a directory containing one of the above files. If "ECM" provides a
separate development package or SDK, be sure it has been installed.

I'm on Arch Linux.

I'm not sure if it's a bug, but after checking the "ActiveMaximizedWindow" option, when I go to edit the default plasma panel, it no longer appears for editing, so I have to remove the panel and create a new one for editing.

Working perfectly: https://i.imgur.com/XNysw3F.png
When editing panel (does not show for editing): https://i.imgur.com/X8yT2hy.png

Garuda linux
Plasma 6

Hey!
First of all thanks for updating this applet for Plasma6!

Always since I first used this applet I missed one feature:
Keep the buttons visible when a window on the same screen is maximized but a window on another screen is focused.
Should a non-maximized window be opened on the same screen, then the buttons should fade out of course.

Basically: Apply button actions and their fade-in & fade-out only for the screen the applet is on.

Currently you always need to focus the window on your second screen, wait for the buttons to fade in and only then you are able to minimize or close the window.
With this feature you could just instantly click on the buttons, without needing to focus the application first.

I'm not sure how easily implementable this currently is, but I wanted to suggest it nonetheless.

This plasmoid is often used in conjunction with borderless maximized windows, where a panel acts as a sort of replacement for the titlebar, so an option to always target the topmost visible maximized window would be a nice addition.

Not sure how to handle "always on top" and "always behind" windows.

Old version of applet used to have an option to choose decorations from list of installed plasma window decorations.
This version has this option as a select window, but the list is empty, so widget buttons style is only inherited from the currently chosen decorations within system settings.
It would be great to restore such an ability as it breaks certain setups.
Nevertheless, thanks for your work to port this and other widgets to Plasma 6. Keep up!

Im not sure, but I believe that uploading the widget to https://store.kde.org makes it available for installation to users, without having to build it.

Currently only old plasma5 version is available there: https://www.pling.com/p/1906579/