Internal crossreferences in the FreeBSD handbook using crossref: are currently broken on PDF output. The official docs [0] say to use <<here-is-the-xref>>. Most xrefs are already written in that notation, they are clean and work great. Update the rest of the remaining xrefs in this chapter to this notation.
[0] : https://docs.asciidoctor.org/asciidoc/latest/macros/xref/
Related bug : https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=266107
Similar fix for boot : https://reviews.freebsd.org/D46263
Similar fix for bsdinstall : https://reviews.freebsd.org/D46262
Similar fix for audit : https://reviews.freebsd.org/D46261
Similar fix for basics : https://reviews.freebsd.org/D46260
Similar fix for advanced networking : https://reviews.freebsd.org/D46258