At the bottom you'll find a shell script to convert and install TTF, OTF, or Type1 fonts, making them available for use with Groff, whose default installation doesn't offer many options. The script uses fontforge fontforge to perform the conversion.
I fully edited my three novels using GNU roff, including graphics and covers.
I used plain roff, I wrote my own macros, which I have refined over the years. For example, this is the tmac file (t-mac: troff-macro) I wrote to format my novels. I also wrote a shell script to convert my roff file to HTML, which, by the way, considering that I accomplished that with just plain HTML and CSS, makes me wonder what the point and purpose of ebook formats is, which besides their obviously inferior formatting quality are cumbersome to navigate, ten times heavier and require special applications to be read and edited (not to mention the closed-source ones, which further complicate the process.)
I used basic roff, wrote my own macros, which I've been perfecting over the years. For example, this is the tmac file (t-mac: macro troff) that I designed to format my novels, here you can appreciate the result. I also wrote a shell script to convert my roff file to HTML, and this is the result. Good opportunity to comment the following: you will notice that there is no great difference in quality between the PDF and the HTML. Surprise what can be achieved with only HTML and cascading styles, right? What leads one to wonder, what is the raison d'etre of ebook formats?!, in addition to their obvious lower format quality they are uncomfortable to navigate, heavier and demand dedicated applications to be read and edited (not to mention those of closed code, which further complicate the procedure).
Back to the subject of Groff. I'm not necessarily an aesthete, but lately, bored with the Times font, the one that comes in groff and its used by default with postscript output, I wanted to try Georg Duffner's EBGaramond, which I think is more pleasant for a novel, and what's more important, being rounder and not having the vertical strokes too highlighted, as is the case of the Times, it better hides the gaps in justified text.
Searching the web for how to convert and install new fonts in groff I found three shell scripts. A first, from Peter Schaffter (the author of groff mom macros,) which comes with a detailed explanation, a second one which is an understandable attempt to simplify Schaffter's script, and a third one from which I don't include a link since it doesn't even deserve you to take a look. From all that information I distilled what I found effective in my own script (pasted at bottom.)
#!/bin/sh
# groff-install-font.sh - (c) 2023 Walter Alejandro Iglesias
#
# Convert and install OTF, TTF or PFA font to use it with Groff. You need
# fontforge installed.
# Directory where you want the font installed (a custom path needs to
# be added to GROFF_FONT_PATH). To install the font in the default
# system wide groff location just leave this empty (you'll need to run
# this script as root in this case).
sitefont=$XDG_DATA_HOME/groff/site-font
prefix=/usr/local/share/groff
if [ "`uname`" = "Linux" ]; then
prefix=/usr/share/groff
fi
if [ "$sitefont" = "" ]; then
sitefont=$prefix/site-font
if [ "`whoami`" != "root" ]; then
echo "You must be root to install the font in $sitefont"
exit 1
fi
elif [ ! -d $sitefont/devps ] || [ ! -d $sitefont/devpdf ]; then
mkdir -p $sitefont/dev{ps,pdf}
fi
if ! echo $1 | grep -E '.*(R|I|B|BI)+$' ||
! echo $2 | grep -E '\.(otf|ttf|pfb)$'; then
echo "Usage: `basename $0` <groffname> <fontfile>.(otf|ttf|pfb)"
echo " groffname must be <name>(R|I|B|BI)"
exit 1
fi
which fontforge >/dev/null 2>&1 || {
echo "This script uses fontforge to convert fonts"
exit 1
}
textmap=$prefix/current/font/devps/generate/textmap
enc=$prefix/current/font/devps/text.enc
groffname=$1
font=$2
name=`basename "$font" | sed -E 's/\.(otf|ttf|pfb)$//'`
fontforge -lang=ff -c "Open(\"$font\");Generate(\"$name.pfa\");"
fontforge -lang=ff -c "Open(\"$font\");Generate(\"$name.t42\");"
afmtodit -e $enc $name.afm $textmap $groffname
if ! grep -q '^ligatures' $groffname ; then
sed -i '/kernpairs/i\
ligatures fi fl 0\
\
' $groffname
fi
mv $name.t42 $groffname $sitefont/devps
mv $name.pfa $sitefont/devpdf
rm $name.afm
ln -s $sitefont/devps/$groffname $sitefont/devpdf/$groffname
printf "$name\t$name.t42\n" >> $sitefont/devps/download
printf "\t$name\t$name.pfa\n" >> $sitefont/devpdf/download
# End of groff-install-font.sh