Well as an alternative method, i used a CUPS PDF printer ( https://www.cups-pdf.de/ ) and I changed the ghostscript prams adding " -dSubsetFonts=false " to the default command.
Now the command is
GSCall %s -q -dCompatibilityLevel=%s -dNOPAUSE -dBATCH -dSAFER -sDEVICE=pdfwrite -sOutputFile="%s" -dAutoRotatePages=/PageByPage -dAutoFilterColorImages=false -dColorImageFilter=/FlateEncode -dPDFSETTINGS=/prepress -dSubsetFonts=false -c -f %s
After this modification, printing on the PDF printer shows that the fonts are fulli embedded (the “sub” column with value “no”)
mirto@bianco500:~/APPOGGIO$ pdffonts hosepla_book.odt__le-job_216.pdf 
name                                 type              encoding         emb sub uni object ID
------------------------------------ ----------------- ---------------- --- --- --- ---------
LiberationSans-Bold~6ae              TrueType          WinAnsi          yes no  yes      7  0
LiberationSans~6af                   TrueType          WinAnsi          yes no  yes      9  0
LiberationSerif~6b0                  TrueType          WinAnsi          yes no  yes     15  0
LiberationSerif-Bold~6b1             TrueType          WinAnsi          yes no  yes     21  0
LiberationSerif-Italic~6b2           TrueType          WinAnsi          yes no  yes     24  0
[none]                               Type 3            Custom           yes no  no      42  0
LiberationMono-Bold~6ac              TrueType          WinAnsi          yes no  yes     60  0
LiberationMono~6b3                   TrueType          WinAnsi          yes no  yes     58  0
[none]                               Type 3            Custom           yes no  no     391  0
DejaVuSansMono~6ad                   TrueType          Custom           yes no  yes    392  0
[none]                               Type 3            Custom           yes no  no     439  0
[none]                               Type 3            Custom           yes no  no     506  0
[none]                               Type 3            Custom           yes no  no     536  0
[none]                               Type 3            Custom           yes no  no     592  0
mirto@bianco500:~/APPOGGIO$ 
It should be wonderful if we can change the gs parameters in Writer