I can confirm that EMF doesn't work for me either on linux.
We have done some work to have EMF work again on both Windows and linux, see bug #55906, so this used to work on both platforms earlier this year.
It looks like an issue upstream in pstoedit and/or ghostscript since reverting Octave to the following cset doesn't work anymore:

changeset:   26932:aa9745a1114a
branch:      stable
parent:      26928:3e6aa7c7bbbb
user:        Pantxo Diribarne <pantxo.diribarne@gmail.com>
date:        Fri Mar 15 23:41:48 2019 +0100
summary:     Feed fig2dev with PDF files converted from svg (bug #55906)

I tried to feed pstoedit with the "-psarg -dNOSAFER" option (as suggested in [1]), but still emf files look empty in libreoffice.

[1] https://sourceforge.net/p/pstoedit/patches/3/

Running  ubuntu 18, for case #4 (eps) and case #5 (epsc)


In Octave 6.0.0:

I see the same 0 sized files for case #14 (emf) and case #15 (meta), so at least those are not a windows only issue.

It is using the pstoedit command same as windows, and unable to redirect binary output on the pstoedit version used.


In Octave 5.1.0:

I see no files  - using pstoedit - the binary output issue


Windows also uses the pstoedit pipelines with fig2dev, but since fig2dev is just going to get an empty file, it still ends up with a 0 sized file

And window, fig files:

$ pstoedit.exe -ssp -f fig 6-ps.ps
pstoedit: version 3.74 / DLL interface 108 (built: Dec  9 2019 - release build -
 g++ 9.2.0 - 32-bit) : Copyright (C) 1993 - 2019 Wolfgang Glunz
#FIG 3.2
Portrait
Flush left
Inches
Letter
100.00
Single
0
1200 2
running-win command line: gs.exe -q -dDELAYBIND -dWRITESYSTEMDICT -dNODISPLAY -d
NOEPS C:/Octave/OCTAVE~4.0/tmp/psin3

 *** WARNING - you have selected SAFER, indicating you want Ghostscript
               to execute in a safer environment, but at the same time
               have selected DELAYBIND. Unless you use this option with
               care (and specifically, remember to call .bindnow) it is
               possible that malicious code may be able to evade the
               limited security offered by the SAFER option.

 *** WARNING - you have selected SAFER, indicating you want Ghostscript
               to execute in a safer environment, but at the same time
               have selected WRITESYSTEMDICT. Unless you use this option with
               care and specifically, remember to execute code like:
                      "systemdict readonly pop"
               it is possible that malicious code may be able to evade the
               limited security offered by the SAFER option.
Error: /invalidfileaccess in --file--
Operand stack:
   false   outstream   (C:/Octave/OCTAVE~4.0/tmp/psout2)   (w)
Execution stack:
   %interp_exit   .runexec2   --nostringval--   --nostringval--   --nostringval-
-   2   %stopped_push   --nostringval--   --nostringval--   --nostringval--   fa
lse   1   %stopped_push   1973   1   3   %oparray_pop   1972   1   3   %oparray_
pop   1960   1   3   %oparray_pop   1817   1   3   %oparray_pop   --nostringval-
-   %errorexec_pop   .runexec2   --nostringval--   --nostringval--   --nostringv
al--   2   %stopped_push   --nostringval--
Dictionary stack:
   --dict:1174/1684(G)--   --dict:0/20(G)--   --dict:133/200(L)--
Current allocation mode is global
Last OS error: Permission denied
Current file position is 7885
GPL Ghostscript 9.50: Unrecoverable error, exit code 1
Could not open file C:/Octave/OCTAVE~4.0/tmp/psout2 in grep
The interpreter seems to have failed, cannot proceed !

Perhaps related: on my ubuntu 18 machine, running print coverage with octave 6, case #14 (emf) and case #15 (meta) are also empty

Running on that machine a test:


pstoedit -ssp -f emf test.ps > test.emf


where test.ps is a valid ps file, and the above command is basically the same as the pipeline I see in ubuntu, it prints an error:


The driver for the selected format cannot write to standard output because it writes binary data