This is probably a pretty basic question, but how do I find out the name
of the font that \definefontfamily expects in the third argument?

For example,
\definefontfamily [dejavu] [serif] [DejaVu Serif]
works fine and sets the text in DejaVu Serif, but that’s not a name I
can find with mtxrun –scripts font:

ellen% mtxrun --script fonts  --list --all --pattern='*DejaVu*'|wc -l
28
ellen% mtxrun --script fonts  --info --list --all --pattern='*DejaVu*'|grep -i "DejaVu Serif"|wc -l
0



mtxrun --script fonts --info for Deja Vu doesn't
show that identifier anywhere. I want to find out what, for example,
Bookman is called.

\definetypeface [five] [rm] [serif] [bookman]
works fine and sets the text in some font that sure looks a lot like
Bookman to my eyes, but
\definefontfamily [five] [serif] [bookman]
doesn’t work at all and the text doesn’t show up.

ellen% mtxrun --script fonts  --list --all --pattern='*bookman*'|wc -l
5

I’ve looked all over for this... even tried understanding font-sel.mkvii
(with mediocre success).

Extra thanks if there’s a way to get ligatures and protrusion to work for it.