cpcnw As pictured below (complete menu is on Arch) the line drawing characters are missing?
Yes, and, no. There're a few things wrong in all this:
If you use UTF-8 chars. (like your dashes and chevrons) in ~/.twmrc, then you have to use an UTF-8 locale for twm to recognize them as valid.
The MenuFont you're using ends in -iso8859-1
This will not have the glyphs for the Unicode code-point (U+2014) that you're trying to print.
Any -*-iso8859-1 font will only have 256 glyphs. You need to use the -*-iso10646-1 fonts if you want Unicode code-points.
cpcnw Oddly the following shows Dejavu Sans-12 at the top?
xfd -fa -adobe-helvetica-medium-r-normal--12-180-----iso8859-1
Because -adobe-helvetica-... isn't a TrueType font, so the default (DejaVu it appears on OpenBSD) is assumed. Use -fn for bitmap fonts.
cpcnw export LC_CTYPE=en_GB.UTF-8 works and shows the line drawing chars
Any UTF-8 locale should work here.
cpcnw export LC_CTYPE=en_GB does not
It won't because en_GB is not a valid locale in OpenBSD, and so the default locale, C, will be used--which is what's used anyway when there's no explicit locale set--and then you run into issue 1), above.
