Addprocs(["ip.ip.ip.ip"], ...) hangs on Windows, works on Linux VM on same machine

I have 3 Julia instances, Windows, Linux in a QEMU VM on the same machine and remote Linux.

I mention the Remote / VM thing to eliminate network issues.
The same happens from the Windows machine to the VM.

Julia on Windows connects, authenticates (twice) and then hangs

In the QEMU to the remote machine

julia> addprocs([Rlinux], tunnel=true)
2-element Vector{Int64}:
 3
 4
julia> @everywhere addxy(x, y) = x + y
julia> @everywhere curry(f, y) = x->f(x, y)
julia> pmap(curry(addxy, 15), 1:5)
5-element Vector{Int64}:
 16
 17
 18
 19
 20

In Windows the same request just hangs.

The same requests with ssh_flags=-vvv

QEMU

# mostly same up to here
debug2: exec request accepted on channel 0
debug2: channel 0: read<=0 rfd 4 len 0
debug2: channel 0: read failed
debug2: channel 0: chan_shutdown_read (i0 o0 sock -1 wfd 4 efd 6 [write])
debug2: channel 0: input open -> drain
debug2: channel 0: ibuf empty
debug2: channel 0: send eof
debug3: send packet: type 96
debug2: channel 0: input drain -> closed
1-element Vector{Int64}:
 2

Windows

# mostly same up to here
debug2: exec request accepted on channel 0
debug3: receive packet: type 98
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug3: receive packet: type 98
debug1: client_input_channel_req: channel 0 rtype eow@openssh.com reply 0
debug2: channel 0: rcvd eow
debug2: channel 0: close_read
debug2: channel 0: input open -> closed
debug3: receive packet: type 96
debug2: channel 0: rcvd eof
debug2: channel 0: output open -> drain
debug2: channel 0: obuf empty
debug2: channel 0: close_write
debug2: channel 0: output drain -> closed
debug3: receive packet: type 97
debug2: channel 0: rcvd close
debug3: channel 0: will not send data after close
debug2: channel 0: almost dead
debug2: channel 0: gc: notify user
debug2: channel 0: gc: user detached
debug2: channel 0: send close
debug3: send packet: type 97
debug2: channel 0: is dead
debug2: channel 0: garbage collecting
debug1: channel 0: free: client-session, nchannels 1
debug3: channel 0: status: The following connections are open:
  #0 client-session (t4 r0 i3/0 o3/0 fd -1/-1 cc -1)

debug3: send packet: type 1
debug3: fd 0 is not O_NONBLOCK
debug3: fd 1 is not O_NONBLOCK
Transferred: sent 2088, received 2924 bytes, in 65.7 seconds
Bytes per second: sent 31.8, received 44.5
debug1: Exit status 1
# and hangs

I’ve tried different sshs builds but that made no difference

C:\Users\matt\Git\usr\bin\ssh.exe # OpenSSH_8.8p1, OpenSSL 1.1.1l 24 Aug 2021

C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\Common7\IDE\CommonExtensions\Microsoft\TeamFoundation\Team Explorer\Git\usr\bin\ssh.exe # OpenSSH_8.7p1, OpenSSL 1.1.1k 25 Mar 2021

C:\Users\matt\AppData\Local\Atlassian\SourceTree\git_local\usr\bin\ssh.exe # OpenSSH_8.4p1, OpenSSL 1.1.1j 16 Feb 2021

The Linux one is OpenSSH_8.4p1 Debian-5, OpenSSL 1.1.1k 25 Mar 2021