Newbi: Unable to achieve mouse behavior stated in nvim documentation

System:
nvim verison 0.4.4
Debian-11, KDE, Konsole

I’m unable to achieve the mouse behavior stated in the nvim documentation.

Desired mouse behavior in nvim (terminal nvim, not GUI nvim-qt):

  1. left-click mouse to “place cursor” at current mouse position
  2. left-drag mouse to “select text”
  3. right-click mouse to “popup” a menu containing “Copy” and “Paste”
  4. selecting popup menu “Copy” will copy selected text into system clipboard
  5. selecting popup menu “Paste” will copy system clipboard at current cursor position

(I’ll skip configuring the clipboard for now (":set clipboard+=unnamedplus") and focus only on configuring the mouse).

From reading the nvim documentation, this mouse behavior appears to be achieved by:
:behave mswin
or
:set mousemodel=popup

Unfortunately, when I tested these options (“init.vim” contains only “:set mousemodel=popup” or “:behave mswin”),

  • left-click mouse FAILS to “place cursor” at current the mouse position.
  • In fact, left-click mouse has NO effect on the cursor position.

Next, the nvim documentation gave another option:
:set mouse=a

Unfortunately, when I tested this option (“init.vim” contains only “:set mouse=a”), I’m unable to “Copy”:

  • left-click mouse places the cursor. ← GOOD!
  • left-drag mouse selects text. ← GOOD!
  • SHIFT-right-click produces popup menu ← NOT right-click, but instead SHIFT-right-click
  • But popup menu lacks “Copy” option ← “Paste” present, but “Copy” missing

Finally, I tried combinations of these options in “init.vim”, but they all failed in some manor.
For example (one of many combinations tried):

 set mouse=a           "left-click mouse places cursor.  SHIFT-right-click yields popup menu, but lacks "Copy"
 behave mswin          "left-click mouse FAILS to place cursor. 
"behave xterm          "left-click mouse FAILS to place cursor.
 set mousemodel=popup  "left-click mouse FAILS to place cursor.
"set mousemodel=extend "left-click mouse FAILS to place cursor.

What am I doing wrong?

Any help appreciated.

P.S. For reference, below are the nvim documentation pages for these mouse options:

--------------------------------------------------------------------------------
								*:behave* *:be*
	:be[have] {model}	Set behavior for mouse and selection.  Valid
				arguments are:
				   mswin	MS-Windows behavior
				   xterm	Xterm behavior

				Using ":behave" changes these options:
				option		mswin			xterm	~
				'selectmode'	"mouse,key"		""
				'mousemodel'	"popup"			"extend"
				'keymodel'	"startsel,stopsel"	""
				'selection'	"exclusive"		"inclusive"


--------------------------------------------------------------------------------
						'mousemodel' 'mousem'
'mousemodel' 'mousem'   string  (default "extend")
                        global
        Sets the model to use for the mouse.  The name mostly specifies what
        the right mouse button is used for:
           extend       Right mouse button extends a selection.  This works
                        like in an xterm.
           popup        Right mouse button pops up a menu.  The shifted left
                        mouse button extends a selection.  This works like
                        with Microsoft Windows.
           popup_setpos Like "popup", but the cursor will be moved to the
                        position where the mouse was clicked, and thus the
                        selected operation will act upon the clicked object.
                        If clicking inside a selection, that selection will
                        be acted upon, i.e. no cursor move.  This implies of
                        course, that right clicking outside a selection will
                        end Visual mode.
        Overview of what button does what for each model:
        mouse               extend              popup(_setpos)
        left click          place cursor        place cursor
        left drag           start selection     start selection
        shift-left          search word         extend selection
        right click         extend selection    popup menu (place cursor)
        right drag          extend selection    -
        middle click        paste               paste

--------------------------------------------------------------------------------
						*'mouse'* *E538*
'mouse'			string	(default "")
			global

	Enables mouse support. For example, to enable the mouse in Normal mode
	and Visual mode: >
		:set mouse=nv
<
	To temporarily disable mouse support, hold the shift key while using
	the mouse.

	Mouse support can be enabled for different modes:
		n	Normal mode
		v	Visual mode
		i	Insert mode
		c	Command-line mode
		h	all previous modes when editing a help file
		a	all previous modes
		r	for |hit-enter| and |more-prompt| prompt

	Left-click anywhere in a text buffer to place the cursor there.  This
	works with operators too, e.g. type |d| then left-click to delete text
	from the current cursor position to the position where you clicked.

	Drag the |status-line| or vertical separator of a window to resize it.

	If enabled for "v" (Visual mode) then double-click selects word-wise,
	triple-click makes it line-wise, and quadruple-click makes it
	rectangular block-wise.

	For scrolling with a mouse wheel see |scroll-mouse-wheel|.

	Note: When enabling the mouse in a terminal, copy/paste will use the
	"* register if possible. See also 'clipboard'.

	Related options:
	'mousefocus'	window focus follows mouse pointer
	'mousemodel'	what mouse button does which action
	'mousehide'	hide mouse pointer while typing text
	'selectmode'	whether to start Select mode or Visual mode

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