Some projects keep surprising me with their “solutions,” and this is one of those cases. A proposal under review by developers from GNOME and Mozilla could change how middle-mouse-button paste behaves on Linux and other Unix-like systems.
The discussions, visible in Mozilla’s Phabricator revision D277804 and a linked GNOME gsettings-desktop-schemas merge request, focus on disabling the traditional primary selection paste by default.
Mozilla proposes changing the default behavior of the Firefox browser on Unix builds so that pressing the middle mouse button no longer pastes text by default. The author of the revision frames the current behavior as a source of confusion and accidental pastes, especially when users press the middle button without expecting the clipboard contents to be inserted into text fields.
There are two clipboards in X11 - but MMB pastes from the selection not the clipboard. I have never heard of the other clipboard being used for anything and I first heard of this more than 30 years ago. (I don’t know what wayland does about clipboards, butiit acts live X11)