MacPorts X11 forwarding when ssh from mac into linux

[AntonioSun]

At my Mac my DISPLAY is of format /private/tmp/com.apple.launchd.xxx/org.macports:0, set by macports. When ssh into linux, the DISPLAY is blank (X11 forwarding is lost, despite that I've use the -X on commandline). My linux side is fine (tested & verified), the problem is at the mac end -- The DISPLAY environment variable on my Mac is set to a local socket, but when SSH into the Linux system, it's not being forwarded correctly -- Linux is expecting the familiar display name of hostname:displaynumber.screennumber yet it's empty.

How to fix the problem pls?

# On Linux side
$ env | grep DISP | wc
      0       0       0

# On Mac side
$ port installed requested and active | grep xorg
  xorg-server @1.20.11_1 (active)

$ uname -srm
Darwin 23.1.0 arm64

$ sw_vers
ProductName:		macOS
ProductVersion:		14.1.2
BuildVersion:		23B92