Hello, Werner:
Have you tried some diagnostic tests, such as trying to get the PDF
output via DVIPS? I suspect that you are, in fact, more knowledgeable
and experience with ConTeXt than I am, but for what it is worth you may
want to look at: 

	* \setupoutput[dvips,acrobat] (SEE: _Context-The Manual_ (Hans Hagen;
English, page 24))
 	* \showbodyfont[Options] (SEE: _Not-so-short Intro to ConTeXt (_J.
Ataz-Lopez;English, page 114))
 	* $ MTXRUN  (mtxrun  is the _ConTeXt TDS Runner Tool_) command from a
terminal window it has has a large number of options for finding the
fonts installed, and for querying their characteristics (SEE: _Fonts out
of ConTeXt _(Hans Hagen, pg 52 and ff))

Em 

On 2023-04-25 08:50, Werner Schmidt via ntg-context wrote:

> Hi conTeXt folks,
> 
> may I ask again. How could I debug the font typesetting of PDF files with conTeXt?
> 
> Any help is highly appreciated.
> 
> Best Werner
> 
> On April 21, 2023 1:29:18 PM UTC, Werner Schmidt via ntg-context <ntg-context@ntg.nl> wrote: 
> 
>> Hi all,
>> 
>> I'd like to use the commercial Adobe Kepler typeface (Kepler Std - version 2.020) in conTeXt (v2023-04-15) as text (serif) font. Although the font files are loaded correctly (see log below), the generated PDF is unreadable (see attached image).
>> 
>> Notes:
>> - Only serif font (keplerstd-light.otf) is not working. It's not embedded in the generated PDF.
>> - italics and bold fonts are embedded and are rendered well
>> - Can't provide font files because Kepler is a commercial typeface
>> 
>> Do you have any ideas how to debug this issue?
>> 
>> Thanks Werner
>> 
>> log file:
>> mkiv lua stats > loaded fonts: 10 files: fontawesome6freesolid900.otf, frutigernextpro-bold.otf, frutigernextpro-regular.otf, iosevka-term-ss09-light.ttf, keplerstd-light.otf, keplerstd-lightcapt.otf, keplerstd-lightit.otf, keplerstd-semibold.otf, latinmodern-math.otf, lmroman10-regular.otf
>> mkiv lua stats > font engine: otf 3.133, afm 1.513, tfm 1.000, 30 instances, 18 shared in backend, 3 common vectors, 15 common hashes, load time 0.449 seconds
>> Example:
>> 
>> This text can't be read in PDF.par
>> {it However, italics are working.}par
>> {bold Also Bold and bfem BoldItalics!}par
>> input{zapf}
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to the Wiki!
> 
> maillist : ntg-context@ntg.nl / https://www.ntg.nl/mailman/listinfo/ntg-context
> webpage  : https://www.pragma-ade.nl / http://context.aanhet.net
> archive  : https://bitbucket.org/phg/context-mirror/commits/
> wiki     : https://contextgarden.net
> ___________________________________________________________________________________