What did I mess up?

[Dave Close]

Since I had a problem and resolved with the JuiceSSH app on Android a
couple of weeks ago, I've had a new problem with one of my local
machines. Although I've checked everything I remember changing back
then, I can't find the cause and would appreciate a clue or two. (Note,
JuiceSSH is not involved in this problem.)

I have four local machines which should be able to use "ssh -[X|Y]"
to run programs on each other for local display. All have key access
to each other. There are no sshrc or .ssh/rc files on any of them. Yet
the pattern I see is the following (best viewed mono-pitch).

  As my user:                        As root:
        |       To:                        |       To:
        |   M1   M2   M3   M4              |   M1   M2   M3   M4
 From:  +-----------------------    From:  +-----------------------
 M1     |   -    x    x    x        M1     |   -    x    x    x
 M2     |   x    -    o    o        M2     |   o    -    o    o
 M3     |   x    o    -    o        M3     |   o    o    -    o
 M4     |   x    o    o    -        M4     |   o    o    o    -

  ( x: fails, o: works, -: n/a )

Clearly the issue is with M1. I have tried adding an .ssh/rc file as
described in the sshd(8) man page but without any initial processing.
That did not help. M1, M2, and M3 are running X11, M3 is running Wayland.
All machines are Fedora 40 fully up-to-date.

The error shown with "ssh -Xvvv" in all failure cases is,
  debug3: send packet: type 91
  debug2: X11 auth data does not match fake data.
  X11 connection rejected because of wrong authentication.
  debug2: X11 rejected 1 i0/o0
-- 
Dave Close, Compata, Irvine CA      "Knowledge speaks,
dave at compata.com, +1 714 434 7359    but wisdom listens."
dhclose at alumni.caltech.edu           -- Jimi Hendrix