Problem: When the selection bar is over a specific file (e.g. a pdf),
and I press {ENTER} nothing happens; the appropriate viewer does not
display/render the file. If I set "mc" to pause after each command, I
see an error message like...

/tmp/mc-waltdnes/mcext2SGP12: 13: /usr/libexec/mc/ext.d/doc.sh: not found

Solution: After some spelunking, I discovered that there is no
"/usr/libexec/mc/" directory ...BUT... there is directory "/usr/lib/mc".
So I went into the "mc"...

Command ==> Edit extension file

...option. Since vim (my preferred editor) uses slashes as delimiters,
the "escaping" gets a bit ugly. I used the vim command...

:%s/\/usr\/libexec\/mc/\/usr\/lib\/mc/

...to turn "/usr/libexec/mc" into "/usr/lib/mc". 173 hits on 173 lines.
"mc" works properly now, e.g. opening pdf files with mupdf.

This problem did not happen on my Gentoo machine, so I assume it's
Devuan-specific. Who would I file a bug report with?

--
Walter Dnes <waltdnes@???>
There are 2 types of people in this world
1) Those who can extrapolate from incomplete data