Hello,
I got the cambria font and installed it :
The text is in italic !
Thanks
Fabrice
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fab@debian:~$ mtxrun --script font --list "cambria*" --all

resolvers       | trees | analyzing 'home:texmf'
identifier           familyname    fontname            filename
subfont   instances

cambria              cambria       cambria             cambria.ttc    1
cambriabold          cambria       cambriabold         cambriab.ttf
cambriabolditalic    cambria       cambriabolditalic   cambriaz.ttf
cambriaitalic        cambria       cambriaitalic       cambriai.ttf
cambriamath          cambriamath   cambriamath         cambria.ttc    2
cambriamathnormal    cambriamath   cambriamath         cambria.ttc    2
cambriamathregular   cambriamath   cambriamath         cambria.ttc    2
cambrianormal        cambria       cambriaitalic       cambriai.ttf
cambriaregular       cambria       cambria             cambria.ttc    1
fab@debian:~$

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\switchtobodyfont[cambria]
\starttext
\input knuth
\stoptext